Everyday calculators

Daily math made fast: restaurant tips and even bill splits, percentage increase/decrease, sale discounts, sales tax from your rate, road-trip fuel cost, loan payment estimates, exact age from birth date, days between dates, and UTC offset time conversion. No account, no downloads — open a tool, enter numbers, get an answer for errands, shopping, and travel planning.

These are the tools people open on a phone mid-task, so they default to sensible values and recalculate as you type. A few habits make the answers more reliable. Decide whether you are tipping on the pre-tax subtotal or the total including tax, because on a large bill the difference is real and both conventions are in common use. When stacking discounts, apply them in sequence rather than adding the percentages — 20% off followed by 10% off is 28% off, not 30%. Sales tax varies by state, county, and sometimes city, so enter the rate from your own receipt rather than a state-level figure if you want the total to match at the register.