Sinking Fund Calculator

A sinking fund saves a known future expense in equal installments before the bill arrives — property taxes, annual insurance premium, holiday gifts, or a replacement appliance. Unlike an emergency fund for unknown shocks, you name the expense and the date.

At 0% interest, monthly contribution = goal ÷ months until due. With interest on the balance, use the annuity payment formula: PMT = FV × r / ((1 + r)^n − 1) with monthly r from annual rate. Defaults: $1,800 goal in 12 months at 0% → $150/month set aside.

Multiple sinking funds often run in parallel — car registration, vet visit, vacation — each with its own envelope (physical or separate savings sub-account). This calculator handles one goal at a time; sum several runs for total monthly sinking load.

Miss a month and the math breaks unless you extend the timeline or increase remaining payments. The model assumes steady deposits — life happens, so pad with an extra week or round up ($155 instead of $150) for slack.

Common mistakes include confusing sinking funds with emergency funds, keeping sinking cash in checking where it gets spent, and forgetting semi-annual bills (divide annual amount by 6 months of saving, not 12).

Taxes on interest in taxable savings are not modeled. High-yield savings at 4%+ makes interest minor for short horizons — 0% is fine for goals under a year.

Payroll deduction sinking funds (escrow for taxes) mirror the same math — employer withholds each paycheck so the annual bill does not surprise you.

Irregular income earners may save a higher percent in high months to cover sinking goals when slow months arrive — steady contribution assumption may not fit freelancers.

Christmas clubs at credit unions are sinking funds by another name — automatic transfer on payday beats manual transfers you might skip.

When the goal date moves up (wedding moved sooner), divide remaining goal by fewer months for a higher required payment — rerun rather than guessing.

Vacation sinking funds compete with retirement — prioritize dated must-pay goals first so travel does not steal from emergency refill.

Zero-interest goals still benefit from separate accounts — mental accounting reduces accidental spending of earmarked cash.

Annual insurance premium sinking at $150/month beats scrambling for $1,800 in the due month — match months until due to billing cycle.

Holiday sinking spread over 11 months avoids December credit card spikes — start January with months=11 for a December goal.

Partially funded sinking accounts still beat credit card interest — save what you can even if monthly contribution exceeds ideal.

Label sinking fund transfers in your bank app — "car registration" separate from "Christmas" prevents accidental borrowing between goals.

Round monthly contribution up to the nearest $5 — small buffers finish goals slightly early without feeling painful.

Sync sinking due dates with payday — auto-transfer two days after deposit reduces missed contributions.

Combine sinking with envelope budgeting — physical or digital envelopes per goal mirror the same monthly contribution math.

Semi-annual car insurance at $600 needs $100/month over six months, not twelve — match the months field to the billing cycle.

Vacation sinking at $2,400 in eight months needs $300/month — shorten months when the trip moves closer rather than missing the deadline.

Tax refund season can fund sinking goals in one lump — divide refund by remaining months to see if you can skip interim contributions.

Multiple sinking goals sum their monthly lines — total sinking load should fit inside the savings slice of your broader budget.

Quarterly bills like water or trash need months=3 between due dates when saving monthly — align the months field to the actual billing period.

Start sinking funds late by dividing remaining goal by fewer months — the payment rises but beats putting the full bill on a card.

Interest on sinking cash in HYSA slightly lowers required payment — enter your APY today when saving more than six months out for best accuracy and planning.

Limits: single goal, level contributions. Not financial advice. Does not automate transfers or track actual balance versus target.