Free Online Calculators

By using our calculators, you agree to our Terms of Use.

Calcometry is a growing collection of free online calculators — built to help you answer everyday questions with numbers, not guesswork. Whether you are checking fees, sizing a load, or running a quick metric, pick a tool below, enter your inputs, and get an instant result. No account required.

The tools fall into a few broad families. Money tools cover marketplace and payment fees (Etsy, eBay, Stripe, PayPal), pricing and margin math for sellers, loan payments, and personal budgeting. Measurement tools handle unit conversions, cooking quantities, shipping weights, and construction materials. Planning tools cover weddings, events, travel, pregnancy timelines, and pet care schedules. Where a tool is tied to one country’s rules — US payroll withholding, for example — the page says so rather than pretending the math is universal.

Every calculator runs entirely in your browser. Nothing you type is sent to us or stored on a server, so you can put real numbers into a paycheck or fee calculator without creating an account or sharing data. Because the math is local, results appear as you type and the pages stay fast on a phone.

Each page follows the same shape: the calculator first, then an explainer covering how the formula works, a worked example with real numbers, the mistakes people commonly make with that specific calculation, and what the estimate deliberately leaves out. Rate-sensitive pages — marketplace fees, payroll, anything tied to a published schedule — cite the primary source and carry a last reviewed date so you can judge how current the defaults are.

A word on what these tools are not. Calcometry produces estimates for planning and sanity-checking, not authoritative figures. A fee calculator tells you roughly what a platform will keep; your seller dashboard tells you what it actually kept. A paycheck calculator approximates withholding; your pay stub and the IRS tables are the record. Health tools like BMI are screening ratios, not diagnoses. When a decision carries real financial, legal, or medical weight, treat our number as the starting point for a conversation with the relevant professional or official document — never as the final answer.

We are not affiliated with Etsy, eBay, Stripe, PayPal, Amazon, or any other platform named on this site; we reference their published rates so sellers can plan. If you find a stale rate or a broken calculation, the contact link in the footer reaches us directly — corrections to fee schedules and agency cutoffs get priority, because a wrong default is worse than no calculator at all.

Results are estimates for informational purposes only — not professional, financial, legal, or tax advice.

Guides: Marketplace fees · POD pricing · How we source rates

3D printing

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Filament weight, print volume, layer time, line width, and model scale.

Filament Weight

Calculate 3D printer filament weight from length, diameter, and material density. Free filament calculator for PLA, PETG, and ABS.

Print Volume & Fill

Calculate bounding box volume and infill material for a 3D print. Free print volume calculator with US and metric units.

Layer Time

Estimate 3D print time from model height, layer height, speed, and perimeter length. Free rough print duration calculator.

Line Width

Calculate extrusion line width from nozzle size and line-width multiplier. Free 3D printing line width calculator.

Model Scale

Scale 3D model dimensions by percentage and see volume change. Free model scale calculator for 3D printing.

3D Print Pricing

Calculate a selling price for 3D printed products from filament, labor, and other costs. Free detailed or quick total-expense pricing tool.

Astrology calculators

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Sun sign, compatibility, moon & rising signs, mercury retrograde, and synastry scores.

Zodiac Sign

Find your tropical sun sign from your birth date — element, modality, and cusp notes included.

Zodiac Compatibility

Compare two sun signs for traditional element harmony — entertainment only, not relationship advice.

Mercury Retrograde

Check whether Mercury is retrograde on a given date — approximate ranges through 2028.

Moon Sign

Estimate your moon sign from birth date, time, and location using ephemeris calculations.

Rising Sign

Find your rising sign (ascendant) from birth date, time, and birthplace coordinates.

Big Three

See your sun, moon, and rising signs together from birth date, time, and place.

Synastry Compatibility

Simple synastry from two birth dates — sun-sign harmony score for entertainment only.

Automotive

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MPG, car payments, lease vs buy, EV charging, and tire size comparisons.

MPG

Calculate fuel economy as MPG or L/100 km from distance driven and fuel used.

Car Payment

Estimate monthly auto loan payment from amount, rate, and term.

Lease vs Buy

Compare total lease cost vs financed purchase net of resale. Estimate only.

EV Charging Cost

Estimate electricity cost to charge an EV from distance, efficiency, and kWh rate — US or metric.

Tire Size

Compare overall tire diameter from metric tire codes like 205/55R16.

Speedometer Error

Estimate speedometer error when changing tire diameter. Compare stock vs new overall tire size.

RPM to Speed

Calculate vehicle speed from engine RPM, total gear ratio, and tire diameter. MPH or km/h.

Cost Per Mile

Calculate driving cost per mile from fuel economy and gas price, plus optional maintenance. IRS mileage rate cited for reference — not tax advice.

Beauty business

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Salon and lash pricing, nail service rates, and hair color developer mixing ratios.

Salon Service Pricing

Price salon services from product cost, service time, hourly goal, overhead, and target margin.

Hair Developer Ratio

Calculate developer amount and total bowl weight from hair color grams and mixing ratio (1:1, 1:1.5, 1:2).

Lash & Wax Pricing

Price lash extensions, fills, and wax services from supplies, time, overhead, and margin.

Business & seller tools

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Margins, pricing, break-even, POD profit, and reverse fee math for sellers.

Profit Margin

Calculate profit margin and markup from revenue and costs. Free business calculator.

Markup

Calculate selling price from cost and markup percentage. Free pricing tool.

Break-Even

Find break-even units from fixed costs, price, and variable cost per unit.

Product Pricing

Price a product from materials, labor, and target profit margin.

POD Profit

Estimate profit per unit for print-on-demand products after platform fees.

Reverse Fee

Find gross charge needed to receive a target net after percentage and fixed fees.

Redbubble Profit

Estimate Redbubble artist earnings from base price and your markup percentage. Planning estimate — confirm on Redbubble.

Printify Profit

Estimate Printify print-on-demand profit after product, print, shipping, and marketplace fees.

TeePublic Profit

Estimate TeePublic artist earnings from base price and your markup percentage. Planning estimate — confirm on TeePublic.

Etsy Pricing

Price Etsy listings from materials, labor hours, hourly rate, and target margin.

Event Planner Markup

Build an event planning client quote from vendor costs, markup percentage, and day rate.

Christian calendar calculators

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Easter dates, Advent start, and live Easter countdown.

Easter Date

Find Western and Orthodox Easter dates plus Ash Wednesday, Good Friday, and Pentecost for any year. Standard computus — not diocesan tables.

Days Until Easter

Count down to the next Western Easter Sunday from today. Shows “Easter is today” on the day and rolls to next year after Easter passes.

Advent Start

Find the first Sunday of Advent for any year — four Sundays before Christmas. Western liturgical calendar math.

Christmas calculators

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Tree fit, lights, wrapping, dinner timing, ham, prime rib, and days until Christmas.

Days Until Christmas

Count down to Christmas Day from today. Western Dec 25 or Orthodox Jan 7 — live countdown, shopping weekdays, and sleeps until the holiday.

Christmas Tree Height

Find the tallest Christmas tree that fits your room from ceiling height, stand, topper, and clearance. Optional floor width for full vs slim trees.

Christmas Lights

Estimate Christmas light bulbs and strands for a tree (by height and density) or roof outline (by length and spacing). LED vs incandescent watt estimates.

Christmas Ornament

Estimate how many Christmas ornaments and feet of garland you need from tree height, ornaments per foot, and garland wraps.

Christmas Garland

Estimate garland length for stairs, mantel, railing, or wreath size from door width. Drape factor adds slack for swags.

Wrapping Paper

Estimate wrapping paper rolls from box dimensions, overlap, and roll size. US inches or metric centimeters with unit toggle.

Christmas Tree Water

Estimate daily water use from trunk diameter and how often to refill your stand. Based on NC State Extension tree care guidance.

Ham

Plan holiday ham weight from guests, bone-in or boneless portions, cook time for fully cooked vs fresh ham, and when to put it in the oven.

Prime Rib

Plan prime rib roast weight, doneness timing, and oven start from guest count and serve time. USDA FSIS beef guidance.

Stuffing

Estimate stuffing volume and dry mix bags from guest count and cups per guest. Side-dish planning for Christmas dinner.

Christmas Dinner Timing

Back-plan ham, potatoes, and rolls from serve time. Editable cook and rest minutes — warnings when oven temps conflict.

Pie

Estimate pies to bake from guest count and slices per guest. Standard 8-slice pie planning for Christmas dessert.

Cookie Exchange

Plan how many dozen cookies to bake for a holiday cookie swap from guest count and dozens each person brings.

Hot Chocolate

Estimate milk gallons and cocoa packets for holiday parties from mug count and ounces per mug.

Holiday Time Off

Find the longest break using limited PTO days between public holidays. Default US holidays Dec 25 and Jan 1.

Color & design

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HEX/RGB/HSL conversion, WCAG contrast ratio, and rem ↔ px.

Color Converter (HEX, RGB, HSL)

Convert colors between HEX, RGB, and HSL. Free color converter for web design and CSS.

Contrast Ratio

Calculate WCAG contrast ratio between two colors. Free contrast checker for text and UI accessibility.

REM to PX Converter

Convert REM to pixels and pixels to REM using a root font size. Free rem px converter for CSS and web design.

Comparisons

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Side-by-side tools — marketplace fees, salary vs hourly, Roth vs Traditional, and more.

Marketplace Fee Comparison

Compare estimated fees on the same sale across Etsy, eBay, and Shopify (US defaults).

Salary vs Hourly Comparison

Compare a salaried offer to an hourly rate on the same schedule.

Roth vs Traditional IRA

Compare after-tax retirement balance for Roth vs Traditional contributions. Not tax advice.

Metric vs Imperial Comparison

See US customary equivalents for a metric length, weight, or temperature.

Stripe vs PayPal

Side-by-side fee comparison for the same sale.

Construction & home

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Square footage, paint, concrete, roof pitch, tile, and mulch volume.

Square Footage

Calculate room area in square feet or square meters from length and width.

Paint

Paint calculator — room walls from length, width, height, coats, and coverage. Gallons or liters needed. Free estimate.

Concrete

Calculate concrete slab volume in cubic yards or cubic meters from length, width, and depth.

Roof Pitch

Convert roof rise and run to pitch ratio and angle in degrees.

Tile

Estimate floor tiles needed from room size, tile dimensions, and waste — US or metric.

Pool Volume

Estimate swimming pool volume in gallons and liters for rectangular or round pools. Dimensions in feet.

Cooking & kitchen

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Recipe scaling, unit conversions, oven temps, yeast, butter, and thaw times.

Recipe Scaler

Scale any recipe up or down by servings. Enter the original yield, your target yield, and an ingredient amount to get the adjusted quantity.

Cooking Unit Converter

Convert between teaspoons, tablespoons, cups, fluid ounces, and milliliters for any recipe. Free kitchen volume converter.

Cups to Grams Converter

Convert cups to grams for flour, sugar, butter, rice, and more using ingredient-specific weights for more accurate baking results.

Yeast Converter

Convert yeast amounts between instant, active dry, and fresh (cake) yeast using standard baking substitution ratios for bread.

Butter Converter

Butter converter — sticks to cups, tbsp, and grams. 1 stick = ½ cup = 113 g. Free US baking conversion.

Baker's Percentage

Calculate baker's percentage for bread formulas — each ingredient as a percent of total flour weight. Free tool for hydration, salt, and yeast ratios.

Pasta Serving

Calculate how much dry pasta to cook for a group based on the number of guests and your chosen serving size per person, in grams.

Turkey Thaw Time

Calculate safe turkey thawing time in the refrigerator or cold water using official USDA guidelines based on your bird's weight.

Air Fryer Converter

Convert a conventional oven recipe to air fryer settings using the standard −25°F, 80% time rule of thumb for home cooking.

Rice Serving

Calculate how much uncooked rice to cook for a group based on guest count and grams per person. Estimates dry weight in grams, ounces, and cups.

Turkey Size

Estimate whole turkey weight from guest count and pounds per person using common USDA-style Thanksgiving planning guidance. US lb and metric kg.

Meat Per Person

Calculate raw meat to buy for a BBQ or brisket cookout from guest count, pounds per person, and expected cooked yield percentage.

Coffee Brew

Estimate total brewed coffee for a group or calculate coffee grounds from water volume and brew ratio. Switch between crowd planning and ratio modes.

Potato Side Dish

Calculate how many potatoes and how much total weight you need for mashed potatoes or other potato sides based on guest count and grams per person.

Cultural calendar calculators

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Chinese zodiac, lunar new year dates, Korean age, and simplified lunar↔Gregorian conversion.

Chinese Zodiac

Find your Chinese zodiac animal and element from a birth date. Uses Lunar New Year boundaries — entertainment and cultural reference, not fortune-telling advice.

Chinese Zodiac Compatibility

Compare two Chinese zodiac animals for traditional harmony or challenge labels. Entertainment only — not relationship or marriage advice.

Lunar New Year Date

Look up the Gregorian date of Chinese Lunar New Year for years 1990–2030. Festival planning reference — dates from published lunisolar tables.

Korean Age

Calculate traditional Korean age (세는나이) from birth and reference dates. Notes 2023 law reform — international age standard now official in Korea.

Lunar to Gregorian Date

Convert a Chinese lunar year, month, and day to a Gregorian date. Simplified lookup from Lunar New Year — festival planning only, not authoritative almanac data.

Gregorian to Lunar Date

Convert a Gregorian calendar date to Chinese lunar year, month, and day. Approximate estimate from Lunar New Year — not a full lunisolar almanac.

Education

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GPA, weighted GPA, grade targets, final exam scores, and study hours.

GPA

Calculate semester or cumulative GPA from letter grades and credit hours. Free GPA tool.

Weighted GPA

Calculate weighted GPA with honors (+0.5) and AP (+1.0) bonuses. Max 5.0 per course.

Grade Needed

Find the GPA you need this term to reach your cumulative target.

Final Exam Grade

Calculate the final exam score you need to reach your target course grade.

Study Hours

How many study hours per week? Enter credit load and hours-per-credit — see weekly and semester study time for college planning.

Percentage to Letter Grade

Convert a percentage score to a letter grade using your own A/B/C/D cutoffs. Default US-style thresholds.

Exam Curve

Scale an exam score using z-scores: map class mean and spread to a new target mean and standard deviation.

Speech Time

How long is my speech? Divide word count by speaking rate — get presentation length in minutes (default 130 WPM). Free instant estimate.

Engineering & science

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Ohm's law, density, molarity, binary/hex, and scientific notation.

Ohm's Law

Calculate voltage, current, or resistance using V = I × R.

Density

Calculate density from mass and volume (ρ = m/V).

Molarity

Molarity (M) from solute mass, molar mass, and volume in liters — moles ÷ L. Free chemistry lab calculator.

Binary & Hex Converter

Convert decimal numbers to binary and hexadecimal.

Scientific Notation

Convert numbers to and from scientific notation.

Gear Ratio

Calculate gear ratio from driver and driven teeth and find output RPM from input speed.

Mechanical Advantage

Calculate ideal mechanical advantage from effort arm and load arm lengths on a lever.

Voltage Drop

Estimate DC voltage drop in copper wire from current, one-way length, and cross-section. Not a code compliance tool.

Resistor Divider

Calculate output voltage from a two-resistor divider: Vout = Vin × R2 / (R1 + R2).

Battery Life

Estimate battery runtime from capacity (mAh) and load current (mA). Hours = mAh ÷ mA for ideal DC loads.

Everyday calculators

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Tips, percentages, discounts, dates, and other handy day-to-day math.

Tip

Calculate tip amount, total bill, and per-person split. Free instant gratuity calculator.

Percentage

Calculate percentages: what is X% of Y, percent change, increase or decrease. Free online tool.

Discount

Calculate sale price and savings from a discount percentage. Free discount tool.

Sales Tax

Estimate sales tax and total price from subtotal and tax rate. Free quick estimate.

Fuel Cost

Trip fuel cost from distance, MPG or L/100km, and fuel price. US gallons or metric liters — free driving cost estimate.

Loan Payment

Estimate monthly loan payment from principal, interest rate, and term. Not a mortgage offer.

Age

Calculate exact age in years, months, and days from a birth date. Free age calculator.

Date Difference

Calculate days, weeks, and months between two dates. Free date calculator.

Time Zone Converter

Convert time between UTC offsets for travel and remote meetings. Does not adjust for DST.

Age Difference

Find the age gap in years, months, and days between two birth dates. Shows who is older and by how much.

Appliance Energy Cost

Estimate monthly electricity cost from appliance wattage, hours of use, and your kWh rate. Planning estimate using EIA average rates.

Sleep Cycle

Find wake times aligned to ~90-minute sleep cycles from your bedtime. General wellness estimate — not medical advice.

Unit Price

Compare unit prices of two package sizes to find the better deal. US or metric quantity labels.

Biorhythm

Chart biorhythm cycles from your birth date for any target day. Entertainment only — not medical or scientific advice.

Biorhythm Compatibility

Compare two birth dates on a target day using classic biorhythm curves. Entertainment only — not relationship or medical advice.

Fee calculators

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See listing fees, transaction cuts, and net payout before you price a product or accept a payment.

Etsy Fee

Listing, transaction, processing, and offsite ads fees.

Amazon FBA

Estimate referral fees, FBA fulfillment, and net profit.

Stripe Fee

Processing fees and net payout for online payments.

eBay Fee

Final value fee and order fee breakdown.

PayPal Fee

Goods & services and checkout fee estimates.

Shopify Fee

Plan cost plus payment processing per order.

Upwork Fee

Freelancer service fee and take-home pay.

Fiverr Fee

Seller fee and net earnings.

Gumroad Fee

Platform and payment processing fees.

Poshmark Fee

Flat fee under $15 or 20% commission on higher sales.

Mercari Fee

Selling and payment processing fee estimates.

Depop Fee

Platform and payment fees for fashion resale.

TikTok Shop Fee

Referral fee, affiliate commission, and net profit for TikTok Shop sellers.

Stripe vs PayPal

Side-by-side fee comparison for the same sale.

Fiber & craft

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Yarn yardage, crochet pricing, quilt fabric, cross-stitch, and embroidery thread.

Yarn Yardage

Estimate yarn yardage and skeins from project size and yarn weight. Free crochet and knitting yarn calculator.

Craft Pricing

Price handmade crafts from materials, labor, and target margin. Free crochet and knit pricing calculator for Etsy sellers.

Quilt Fabric

Estimate quilt top, backing, binding, and total fabric yardage. Free quilting fabric calculator for yardage planning.

Cross-Stitch Fabric

Calculate cross-stitch fabric dimensions from stitch count and fabric count. Free aida and evenweave fabric size calculator.

Embroidery Thread

Estimate embroidery floss length and skeins from stitch count. Free thread yardage calculator for hand embroidery.

Fitness estimates

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BMI, healthy weight range, heart rate zones, and water intake — estimates only.

BMI

Calculate BMI from height and weight. Estimate only — not medical advice.

Ideal Weight

Estimate healthy weight range from height using BMI 18.5 to 24.9. Not medical advice.

Heart Rate Zone

Estimate max heart rate and training zones by age. Not medical advice.

Water Intake

Estimate daily water needs from body weight and exercise. General guideline only.

One Rep Max

Estimate your one-rep max (1RM) from submaximal weight and reps using the Epley formula. Training estimate only.

Training Volume

Calculate training volume (tonnage) from sets, reps, and load. Free strength training math tool.

Steps to Miles

Convert daily step count to miles or kilometers using your stride length. US or metric stride input.

Protein Intake

Estimate daily protein needs from body weight and activity level. General guideline — not medical or nutrition advice.

Freelancer rates

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Hourly rates, project quotes, consulting day rates, and retainer pricing.

Hourly Rate

Calculate freelance hourly rate from income goal, billable hours, and expenses.

Project Pricing

Price a fixed project from hours, rate, expenses, and buffer. Free estimate tool.

Consulting Rate

Calculate consulting hourly and day rate from salary target, overhead, and utilization.

Retainer

Calculate monthly retainer from hours, hourly rate, and retainer discount.

Gardening & outdoor

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Mulch volume, raised bed soil, plant spacing, seed coverage, and rainwater yield.

Mulch

Calculate mulch or gravel volume from bed area, depth, and bag size — US or metric.

Garden Bed Volume

Calculate soil or compost volume for raised garden beds from length, width, and depth.

Plant Spacing

Estimate how many plants fit in a bed from dimensions and on-center spacing.

Seed Coverage

Calculate seed quantity from planting area and application rate on the packet.

Rainwater Barrel

Estimate rainwater yield from roof area, rainfall depth, and runoff coefficient.

Genealogy calculators

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Cousin relationship names, generation labels, and ancestor counts.

Family Relationship

Find cousin degree and removal from generations to a shared ancestor. Genealogy reference — simplified chart, not legal kinship proof.

Generation

Look up generational cohort from birth year using Pew Research-style year ranges. Social labels — approximate and debated, not precise identity.

Ancestor Count

Count direct ancestors in a family tree by generations back using 2^(n+1) − 2. Pedigree math — assumes distinct ancestors, not pedigree collapse.

Halloween calculators

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Candy, pumpkins, party punch, yard power, and countdown to October 31.

Days Until Halloween

Count down to the next Halloween (October 31) from today. Shows Happy Halloween on the night and rolls to next year after October 31 passes.

Trick-or-Treat Candy

Estimate Halloween candy for your front door, a classroom party, or neighborhood turnout. Switch door, classroom, or estimate modes with weather adjustments.

Pumpkin Carve Date

Find the earliest carve date so your jack-o'-lantern still looks good on display night. Enter display end date and expected shelf life in days.

Pumpkin Puree

Convert fresh pumpkin weight to cups of puree and standard pie counts. Switch US pounds or metric kilograms with automatic value remapping.

Pumpkin Weight Calculator (OTT)

Estimate giant pumpkin weight from circumference and axis measurements using the Over-The-Top (OTT) formula. US inches or metric centimeters.

Pumpkin Seed

Estimate cups of roasted pumpkin seeds from pumpkin weight, sheet pans needed, and approximate roast time for Halloween leftovers.

Halloween Punch

Estimate total punch volume from guest count, ounces per guest per hour, and party length. Results in fluid ounces, gallons, and liters.

Dry Ice

Estimate dry ice pounds for a fog duration and burn rate. Party planning heuristic only — not a safe exposure dose; see CDC carbon dioxide guidance.

Halloween Display Wattage

Total watts for inflatables and light strands versus a typical 15-amp circuit at 80% load. See if you need extra circuits for outdoor Halloween décor.

Candy Jar

Estimate how many candies fit in a jar from jar volume, packing fraction, and single-piece volume. Includes low–high band for guessing games.

Caramel Apple

Calculate total caramel grams and batch count from apple count, grams per apple, and grams per recipe batch for Halloween treats.

HVAC & home systems

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BTU rule-of-thumb, R-value layers, CFM ventilation, and duct sizing estimates.

BTU

Estimate cooling BTU/h from room area using a rule-of-thumb factor. Not a Manual J load calculation.

R-Value

Sum insulation R-values in layers and find U-factor (1/R). Free building envelope estimate.

CFM

Estimate required CFM from room volume and air changes per hour (ACH). Ventilation rule-of-thumb.

Duct Size

Estimate round duct diameter from CFM and air velocity. Simple HVAC duct sizing estimate.

Investing & returns

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ROI, CAGR, compound interest, dividends, and portfolio rebalancing estimates.

ROI

Calculate return on investment percentage and dollar gain. Not investment advice.

CAGR

CAGR calculator — annualized return from start value, end value, and years held. Free compound growth rate tool.

Compound Interest

Project balance with compound interest and monthly contributions. Estimate only.

Stock Profit

Calculate stock trade profit or loss including fees. Not tax or investment advice.

Dividend Yield

Calculate dividend yield from share price and annual dividend per share.

Rule of 72

Estimate years to double money at a given annual return using the Rule of 72.

DCA

Simulate dollar-cost averaging with fixed monthly investments. Hypothetical returns only.

Inflation

Estimate inflation-adjusted (real) return from nominal return and inflation rate.

Portfolio Rebalance

See how much to buy or sell to hit target portfolio allocation. Not investment advice.

Islamic calendar calculators

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Ramadan dates, days-until countdown, and Hijri ↔ Gregorian conversion.

Ramadan Date

Find Ramadan start and end dates plus Eid al-Fitr for any Gregorian year. Umm al-Qura or tabular Hijri estimate — confirm with local moon sighting.

Days Until Ramadan

Count down to the next Ramadan from today. Shows Ramadan Mubarak on start day and rolls to next year after Eid — Umm al-Qura or tabular estimate.

Hijri Gregorian Converter

Convert between Gregorian and Hijri (Islamic) dates. Umm al-Qura or tabular civil method — planning estimate, not a religious ruling.

Jewish calendar calculators

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Passover & Rosh Hashanah dates and live Passover countdown.

Passover Date

Find when Passover (Pesach) starts on the Gregorian calendar for any year. 7-day Israel or 8-day Diaspora estimate — holidays begin at sunset.

Rosh Hashanah Date

Find Rosh Hashanah (1 Tishrei) on the Gregorian calendar for any year. Hebrew molad-based estimate — begins at sunset.

Days Until Passover

Count down to the next Passover from today. Greeting on start night, day count during the festival, auto roll-forward to next year.

Math & homework

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Fractions, GCF/LCM, statistics, quadratics, geometry, and percentage change.

Fraction

Add, subtract, multiply, or divide fractions and reduce to lowest terms automatically. Free fraction calculator for homework, baking, and everyday math.

GCF and LCM

Find the greatest common factor (GCF) and least common multiple (LCM) of two whole numbers using the Euclidean algorithm. Free math homework helper.

Mean, Median & Mode

Calculate mean, median, and mode from a list of numbers in one step. Paste comma-separated values for quick statistics homework and data summaries.

Standard Deviation

Calculate sample or population standard deviation and variance from any number list. Choose sample (n−1) or population mode for stats homework.

Quadratic Formula

Solve quadratic equations ax² + bx + c = 0 with the quadratic formula. Shows real roots and discriminant — free calculator for algebra homework.

Slope

Find slope and y-intercept of the line through two points using m = (y₂ − y₁)/(x₂ − x₁). Free line equation helper for algebra and graphing homework.

Pythagorean Theorem

Solve for any missing side of a right triangle with the Pythagorean theorem a² + b² = c². Enter two sides; the calculator finds the third instantly.

Triangle Area

Find triangle area from base and height or three side lengths using Heron's formula. Switch modes for geometry homework and construction estimates.

Circle

Circle area and circumference from radius or diameter — π × r² and 2πr. Free geometry calculator with worked examples.

Percentage Change

Percent increase or decrease between two values — shows absolute change and % change. Free price and growth calculator.

Moon & lunar calculators

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Moon phase, next full/new moon, lunar age, and approximate moon rise/set times.

Moon Phase

Find the moon phase, illumination percentage, and lunar age for any date. Synodic-month estimate based on USNO-style astronomy — not for navigation.

Next Full Moon

Find the next full moon on or after any start date. Days-until countdown using a synodic-month estimate — compare with USNO tables for exact times.

Next New Moon

Find the next new moon on or after any date. Days-until countdown for lunar calendars, stargazing, and planning — synodic-month estimate.

Lunar Age

Calculate lunar age in days since the last new moon for any date. Useful for gardening folklore and moon-phase planning — synodic estimate.

Moon Rise & Set

Estimate moonrise and moonset times for a date and location. Uses astronomy-engine style calculations — approximate times for planning only.

Music & audio

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BPM to delay, note frequencies, audio file size, and cents detune.

BPM to Delay

Convert BPM to delay time in milliseconds for quarter, eighth, and dotted notes. Free BPM delay calculator for music production.

Note Frequency

Convert musical note names to frequency in Hz and back. Free note frequency calculator with A4 = 440 Hz tuning.

Audio File Size

Calculate uncompressed PCM audio file size from sample rate, bit depth, channels, and duration. Free audio size calculator.

Cents & Detune

Calculate cents between two frequencies or detune a pitch by cents. Free cents calculator for tuning and intonation.

Numerology calculators

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Life path, expression, soul urge, personal year/month/day numbers, and name math.

Life Path Number

Find your life path number from your birth date using Pythagorean numerology. Master numbers 11, 22, and 33 preserved.

Expression Number

Calculate your expression (destiny) number from your full name using Pythagorean letter values A–Z.

Soul Urge Number

Find your soul urge (heart's desire) number from the vowels in your name — Pythagorean A–Z system.

Personality Number

Calculate your personality number from the consonants in your name using Pythagorean numerology.

Personal Year Number

Calculate your personal year number from your birth date and a calendar year — Pythagorean numerology.

Personal Month Number

Find your personal month number from birth date, calendar month, and year — Pythagorean numerology.

Personal Day Number

Calculate your personal day number from birth date and a target calendar date — Pythagorean numerology.

Numerology Compatibility

Compare two life path numbers (1–9, 11, 22, 33) for traditional Pythagorean numerology compatibility themes.

Name Numerology

Full name numerology chart: expression, soul urge, and personality numbers from one name — Pythagorean A–Z.

Paper & print sizes

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ISO paper dimensions, bleed, book signatures, and pixels to print size.

ISO Paper Size

Look up ISO A, B, and C paper dimensions in mm and inches. Free ISO 216 paper size calculator for A4, A3, and more.

Bleed & Trim

Calculate final print dimensions with bleed added to trim size. Free bleed calculator for print-ready PDFs.

Book Signature

Estimate printer sheets and signatures for a book page count. Free book imposition calculator for print planning.

Pixels to Print Size

Convert pixel dimensions and DPI to print size in inches and millimeters. Free pixels-to-print calculator for designers.

Print Size & DPI

Calculate maximum print size in inches and centimeters from pixel dimensions and target DPI. See whether your photo is large enough for wall prints.

Parties & events

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Baby showers, bridal showers, party food, drinks, cake servings, and quinceañera budgets.

Baby Shower Budget

Split a baby shower budget across venue, food, cake, decor, games, and favors with typical percentage allocations. Planning estimate only.

Baby Shower Food

Estimate total food pounds for a baby shower from guest count, pounds per guest, and a buffer. Splits entrees, sides, and dessert for buffet planning.

Cake Serving

Calculate cake servings from guest count and slice size (party or wedding). Suggests the smallest pan that fits your guest list with a buffer.

Party Drink

Estimate alcoholic drinks, soft drinks, wine bottles, and beer for a party from guest count, hours, and drinker percentage. Rule-of-thumb planning only.

Bridal Shower Budget

Split a bridal shower budget across venue, food, drinks, decor, activities, and other costs with typical percentage allocations. Planning estimate only.

Party Food

Estimate total food pounds for any party from guest count, pounds per guest, and a buffer. Splits entrees, sides, and dessert for buffet or potluck planning.

Quinceañera Budget

Split a quinceañera budget across venue, catering, attire, photography, music, decor, and other costs with typical percentage allocations. Planning estimate only.

Party Favor Budget

Calculate total party favor cost from guest count and cost per favor. Quick budget math for showers, weddings, and birthday parties.

Bridesmaid Dress Split

Split a total bridesmaid dress cost evenly across the wedding party. See per-person share and any rounding remainder.

Florist Stem

Calculate total flower stems for centerpieces and arrangements from arrangement count, stems per piece, and a buffer. DIY and florist planning estimate.

Pizza Party

Calculate how many pizzas to order for a party from guest count, slices per guest, and slices per pizza. Quick headcount math for birthdays and game nights.

Appetizers Per Person

Estimate total appetizer pieces for a cocktail party or open house from guest count, event hours, and pieces per guest per hour.

Ice for Party

Estimate how much ice to buy for a party from guest count and pounds per guest, with US lb and metric kg units and a planning buffer.

Payroll & salary

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Salary ↔ hourly, overtime, paycheck estimates, raises, and cost-of-living.

Salary to Hourly

Convert annual salary to hourly rate from hours and weeks worked per year.

Hourly to Salary

Convert hourly wage to annual and monthly salary.

Overtime

Calculate weekly pay with regular and overtime hours. US 1.5× default.

Paycheck

Estimate net pay from gross and total deduction percentage. Not tax advice.

Raise

See new salary and monthly increase from a raise percentage.

Cost of Living

Compare equivalent salary between cities using COL index numbers you enter.

Childcare Cost

Estimate monthly and annual childcare cost from days per week, weeks per year, and daily rate.

Maternity Leave Pay

Estimate total paid maternity leave from weekly gross pay, paid weeks, and pay percentage.

Personal finance

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Savings goals, emergency fund, debt payoff, budgeting, net worth, and FIRE estimates.

Savings Goal

Find monthly savings needed to reach a financial goal, or project future value from regular contributions at an assumed return. Not financial or tax advice.

Emergency Fund

Calculate an emergency fund target from monthly essential expenses and months of coverage. Popular 3–6 month guideline — not personalized financial advice.

Debt Payoff

Estimate months to pay off a loan, credit card, or other debt with a fixed monthly payment and APR. Shows total interest — planning math only, not financial or tax advice.

Debt Snowball

Model debt snowball payoff: smallest balance first while paying minimums on other debts, plus extra payment. Shows months, interest, and order — not advice.

Debt Avalanche

Model debt avalanche payoff: highest APR first while paying minimums elsewhere, plus extra payment. Often saves interest vs snowball — not financial advice.

50/30/20 Budget

Split take-home income into 50% needs, 30% wants, and 20% savings with the 50/30/20 budgeting rule. Starting template only — not personalized financial advice.

Net Worth

Calculate net worth as total assets minus total liabilities for a quick snapshot. Enter your own numbers — planning estimate only, not financial advice.

Sinking Fund

Calculate monthly savings to reach a sinking fund goal by a target date in months, with optional interest. Plan for holidays, insurance, or large purchases.

FIRE Number

Estimate a FIRE number from annual expenses and a withdrawal rate (default 4% rule of thumb). Illustration only — not financial or retirement planning advice.

Rent Affordability

Estimate maximum affordable rent from monthly income using the percent-of-income rule. HUD-style planning estimate — not financial advice.

Car Affordability

Estimate an affordable car price using the 20/4/10 rule: 20% down, 4-year loan, 10% of income for all car costs. Illustration only.

Pet calculators

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Dog and cat age charts, food costs, boarding, litter boxes, and aquarium volume.

Dog Age

Convert dog years to human years with AAHA size-class charts for small, medium, large, and giant breeds — not the outdated multiply-by-7 rule. Estimate only.

Cat Age

Convert cat years to human years with a common feline age chart used by veterinarians. Planning estimate only — not veterinary advice or a health assessment.

Pet Food Cost

Estimate monthly or annual dog or cat food cost from daily scoops or cans and price per unit. Budget planning only — not veterinary feeding or nutrition advice.

Annual Pet Budget

Sum annual pet ownership costs across food, vet care, insurance, supplies, and other line items. Household budget snapshot — not financial or veterinary advice.

Pet Boarding Cost

Estimate pet boarding cost from nightly kennel rate, number of nights, and flat fees. Budget before travel — rates vary by region, size, and facility amenities.

Litter Boxes Needed

How many litter boxes do you need? Common vet guidance is one box per cat plus one extra. Planning estimate only — not veterinary advice on litter-box behavior.

Aquarium Volume

Calculate aquarium volume in liters and US gallons for rectangular or cylindrical tanks. Switch inches or centimeters. Gross tank size — not fill volume after substrate.

Dog Walking Cost

Estimate dog walking cost from walks per week and rate per walk. Weekly, monthly, and annual totals. Budget planning only — include tips in your per-walk rate.

Pet Age From Birthday

Calculate your pet's calendar age in years, months, and days from a birth date. Different from dog-year charts — generic date math, not veterinary advice.

Dog Food Portion

Estimate daily dog food amount from body weight and activity level using common percentage-of-weight guidelines. Planning only — not veterinary feeding advice.

Cat Food Portion

Estimate daily cat food amount from body weight and activity using common percentage-of-weight guidelines. Planning only — not veterinary feeding advice.

Puppy Weight

Estimate adult dog weight from current puppy weight and age in months. Rough growth projection — not veterinary or breeding advice.

Rabbit Age

Convert rabbit years to human years using a common reference chart. First year ≈ 20 human years, then +6 per year. Planning estimate — not veterinary advice.

Photography

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Depth of field, hyperfocal distance, crop factor, print size, EV, and field of view.

Depth of Field

Calculate near focus, far focus, and total depth of field from focal length, aperture, distance, and sensor size. Free DOF calculator for photographers.

Hyperfocal Distance

Calculate hyperfocal distance from focal length, aperture, and sensor circle of confusion. Maximize sharp depth from near foreground to infinity.

Crop Factor

Find crop factor for common sensor sizes and convert lens focal length to full-frame equivalent. Handy when comparing lenses across camera bodies.

Print Size & DPI

Calculate maximum print size in inches and centimeters from pixel dimensions and target DPI. See whether your photo is large enough for wall prints.

Aspect Ratio

Scale image dimensions to fit a target width and height without cropping or distortion. Keeps the original aspect ratio for resize and layout planning.

Megapixel

Convert pixel width and height to megapixels, or solve dimensions from a target megapixel count and aspect ratio. Useful for camera and print planning.

Exposure Value (EV)

Calculate exposure value (EV) from aperture, shutter speed, and ISO using the standard APEX formula. Compare exposure settings across lighting setups.

Shutter Angle

Convert cinema shutter angle to shutter speed and back at any frame rate. Useful for matching motion blur between video cameras and film-style settings.

Flash Guide Number

Solve flash guide number, flash-to-subject distance, or required f-number with GN = distance × f-number. Free strobe exposure calculator for photographers.

Field of View

Calculate horizontal field of view in degrees from focal length and sensor width. Pick presets for full-frame, APS-C, Micro Four Thirds, and 1-inch sensors.

Photography Session Pricing

Price a photo session from shoot hours, editing time, travel, expenses, and target margin.

TV Viewing Distance

Find recommended TV viewing distance from screen diagonal size. THX-style range for home theater setup.

Pregnancy & due date

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Due date, gestational week, trimester, and IVF due date — calendar estimates only.

Due Date

Estimate pregnancy due date from the first day of your last period and average cycle length using the 280-day rule. Calendar math only — not medical advice.

Pregnancy Week

Find how many weeks and days pregnant you are — and which trimester — from your last period or a known due date. Calendar estimate — not medical advice.

Pregnancy Countdown

Count days remaining until your due date from a reference date. Clinicians may revise the date after ultrasound. Calendar estimate — not medical advice.

Conception Date Estimate

Estimate a rough conception date from your last menstrual period or due date using standard calendar assumptions. Not a fertility predictor or medical advice.

IVF Due Date

IVF due date from embryo transfer date and embryo age (day 3, 5, or 6). Calendar estimate — confirm with your clinic.

Baby Age

Calculate your baby's age in weeks, months, and days from birth date. Infant-focused — not the same as a general age-in-years calculator.

Diapers Needed

Estimate how many diapers you need per year by age band — newborn, infant, or toddler. Rough consumption averages for budgeting and registry planning.

Relationship & fun calculators

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Love percentage, friendship scores, half birthday, anniversary countdown, and duration.

Love

Enter two names for a playful love compatibility percentage. Entertainment only — a name hash game, not scientific or relationship advice.

Friendship Compatibility

Compare two names for a playful friendship compatibility score. Entertainment only — not a measure of real friendship quality.

Half Birthday

Find your next half birthday — six calendar months after your birth date. Date math for fun celebrations, not astrological meaning.

Anniversary Countdown

Count days until your next relationship or wedding anniversary from the original date. Calendar countdown — not a reminder service.

Relationship Duration

Calculate how long you have been together from a start date to today or any end date. Calendar duration — same math as date difference, relationship framing.

Sewing & fabric

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Fabric yardage, weight (GSM), seam allowance, pattern scale, and bias tape.

Fabric Yardage

Calculate fabric yardage and square area from cut length and fabric width. Free sewing calculator for quilt and garment planning.

Fabric Weight Converter

Convert fabric weight between ounces per square yard and GSM (grams per square meter). Free fabric weight converter for sewing and quilting.

Seam Allowance

Add seam allowance to finished pattern dimensions for cutting fabric. Free seam allowance calculator for sewing.

Pattern Scale

Scale sewing pattern dimensions by percentage. Free pattern resize calculator for grading and print scaling.

Bias Tape

Estimate continuous bias tape length from a fabric square and strip width. Free bias binding calculator for quilting and garment finishing.

Shipping & logistics

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Dimensional weight, billable weight, girth, landed cost, and freight class estimates.

Dimensional Weight

Calculate dimensional (DIM) weight and billable shipping weight from package dimensions and actual scale weight using the 139 or 166 divisor.

Cubic Volume

Calculate a box's cubic volume in cubic inches, cubic feet, or cubic centimeters from length, width, and height dimensions.

Volumetric Weight Calculator (Metric)

Calculate international volumetric (chargeable) weight in kilograms from cm dimensions using the standard air freight divisor.

Shipping Cost Estimator

Estimate shipping cost by multiplying your billable weight by a carrier or freight rate per pound or kilogram you enter.

Package Girth

Calculate package girth and length-plus-girth to check whether a box falls within carrier oversize package limits and fees.

Landed Cost

Calculate total landed cost per shipment — product price, shipping, import duty percentage, and other fees, all combined.

Carton Fill

Calculate what percent of a shipping carton's volume is filled by your product quantity and dimensions before you pack it.

Freight Density

Calculate freight density in lb/ft³ and estimate NMFC freight class from weight and volume — starting point for LTL rate planning.

Size converters

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Shoe, clothing, ring, and hat size charts — US, EU, UK, and metric crosswalks.

Shoe Size Converter

Convert shoe sizes between US, EU, UK, and foot length in cm. Men's and women's charts — estimates only; brands vary.

Clothing Size Converter

Convert clothing sizes between US, EU, and UK for tops and dresses. Chart estimates — sizing varies by brand.

Ring Size Converter

Convert ring sizes between US numeric, UK letter, EU circumference (mm), and inner diameter. Free size chart tool.

Hat Size Converter

Convert hat sizes between US fitted sizes and head circumference in cm or inches. Free cap and hat size chart.

Bra Size Converter

Convert bra sizes between US, UK, and EU band and cup systems. Charts vary by brand — estimate only.

CM to Feet & Inches

Convert 175 cm to feet and inches — height in ft/in for US forms and size charts. Free metric-to-imperial calculator.

Sports pacing

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Running pace, race splits, VDOT estimate, swim pace, and bike gearing.

Running Pace

Calculate running pace, finish time, or distance. Free pace calculator for 5K, 10K, half marathon, and marathon training.

Race Split

Calculate even pace splits for a race distance and target finish time. Free running split calculator for 5K to marathon.

VDOT Pace

Estimate VDOT running fitness from a recent race time and distance. Free VDOT calculator — training estimate, not lab VO₂max.

Swim Pace

Calculate swimming pace per 100 meters or yards from time and distance. Free swim pace calculator for pool training.

Bike Gear Ratio

Calculate bicycle gear ratio, rollout, and speed from chainring, cog, cadence, and wheel size. Free cycling gear calculator.

Startup & equity

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Vesting, runway, dilution, SAFE conversion, and SaaS unit economics.

Vesting

Estimate vested shares from grant size, cliff, and vest period. Not legal or tax advice.

Runway

Calculate startup runway from cash balance and monthly burn. Free planning estimate.

Equity Dilution

Estimate founder ownership after a priced round. Simplified cap table math only.

Stock Option

Estimate option spread and paper value from shares, strike, and FMV. Not tax advice.

SAFE

Estimate SAFE conversion shares from cap, discount, and round terms. Simplified model.

SaaS Break-Even

Find customers or units needed to break even on fixed and variable costs.

CAC Payback

Calculate customer acquisition payback period from CAC and gross margin.

LTV to CAC

Estimate customer LTV and LTV:CAC ratio from ARPU, margin, and churn.

Cap Table

Simple cap table with founders, option pool, and investors. Estimate only.

Time & calendar

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Date math, business days, ISO week numbers, FTE hours, and Unix timestamps.

Date Add & Subtract

Add or subtract days, weeks, or months from any date — deadlines, due dates, and scheduling. Free date math calculator.

Business Days

Count business days (Mon–Fri) between two dates. Free weekday calculator — excludes weekends, not public holidays.

Work Hours to FTE

Weekly hours to FTE — full-time equivalent from hours worked. Free staffing and grant FTE calculator.

Week Number

Find the ISO 8601 week number for any date. Free week-of-year calculator for project planning and reporting.

Unix Timestamp Converter

Convert Unix epoch timestamps to human-readable dates and back. Free timestamp converter for developers and log analysis.

Days Until

Count days remaining until a target date from any starting date. Simple countdown for events, deadlines, and vacations.

Date Difference

Calculate days, weeks, and months between two dates. Free date calculator.

Age

Calculate exact age in years, months, and days from a birth date. Free age calculator.

Time Zone Converter

Convert time between UTC offsets for travel and remote meetings. Does not adjust for DST.

Moon Phase

Find the moon phase, illumination percentage, and lunar age for any date. Synodic-month estimate based on USNO-style astronomy — not for navigation.

Next Full Moon

Find the next full moon on or after any start date. Days-until countdown using a synodic-month estimate — compare with USNO tables for exact times.

Days Until

Count days remaining until a target date from any starting date. Simple countdown for events, deadlines, and vacations.

Travel & time

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Currency conversion, trip time, jet lag, and group trip budgets.

Currency Converter

Convert an amount using your own exchange rate. Not live forex data.

Travel Time

How long is the drive? Enter distance and average speed — get trip time in hours and minutes (mph or km/h). Free, instant, no signup.

Jet Lag

Rough estimate of recovery days after crossing time zones. General guideline.

Trip Budget Splitter

Split a group trip total evenly by people and nights.

Trip Budget

Estimate total trip cost from daily budget, flights, lodging, and extras.

Walking Time

Calculate how long a walk takes from distance and pace. Default 3 mph — switch US or metric units.

Unit converters

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Convert length, weight, temperature, and more — metric and imperial, instantly in your browser.

Meters to Miles Converter

Convert meters to miles and miles to meters instantly.

Kg to Lbs Converter

Convert kilograms to pounds and pounds to kilograms.

Celsius to Fahrenheit Converter

Convert °C to °F for weather, cooking, and travel.

Inches to Cm Converter

Convert inches to centimeters and centimeters to inches.

Km to Miles Converter

Convert kilometers to miles for driving and running.

Liters to Gallons Converter

Convert liters to US gallons and back.

Feet to Meters Converter

Convert feet to meters and meters to feet.

Mph to Kmh Converter

Convert miles per hour to kilometers per hour.

Oz to Grams Converter

Convert ounces to grams for cooking, shipping, and nutrition labels.

Mm to Inches Converter

Convert millimeters to inches for 3D printing, bolts, and precision work.

Acres to Hectares Converter

Convert acres to hectares for land, farms, and real estate.

Stone to Kg Converter

Convert stone to kilograms for UK body weight and health records.

Wedding planning

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Budget splits, guest costs, tables, alcohol, catering, tips, and countdown.