Break Christmas, the car, HVAC and other lumpy bills into one calm monthly amount
PMT = (G − S(1+i)n) × i / ((1+i)n − 1)
| Fund | Goal | Saved | Per period | Periods | Deadline | Status |
|---|---|---|---|---|---|---|
| Add a fund to see results | ||||||
| Adjust inputs to see results |
The free Sinking Funds Planner turns irregular, once-a-year (or once-every-few-years) costs into a single regular savings amount. Add each upcoming bill — Christmas, car insurance, HVAC, a vacation — set a deadline and anything already saved, and the planner shows how much to set aside each period, a combined monthly figure, an allocation chart and a month-by-month schedule.
Start with the settings that apply to every fund:
Use a quick-add chip or + Add fund. Each fund needs:
You can park a fund without deleting it by unchecking it. Up to 12 funds can run in one plan. The plan is stored in this browser so a refresh does not wipe it.
Results update as you type. The highlighted figure is the amount to automate at your chosen frequency. Behind it:
The interest-on formula is the standard sinking-fund (uniform-series) payment:
PMT = (G − S(1+i)n) × i / ((1+i)n − 1)
When interest is off, or the rate is zero, it simplifies to:
C = (Goal − Saved) ÷ Periods
Goal: Stop putting the holidays on a card by spreading gifts and travel over the months you actually have.
A 4.5% APY changes a short horizon like this only a little. The value of the planner is the deadline math, not the yield.
Goal: See the combined peak when two annual bills sit on the calendar at once, and the drop after the first one is funded.
The snapshot names the peak months and the date the plan gets cheaper. Use that when you decide whether a vacation fund can start now or should wait until January.
Goal: Compare a plain split against a 4.5% APY sinking fund for a multi-year repair.
On a two-year cash goal, a mid-single-digit APY only shaves a small slice off each deposit. Treat interest as a bonus, not the reason the fund works.
Not Professional Advice: This planner is an estimation and educational tool and does not constitute professional financial advice. Actual costs, savings yields and timing vary. Consult a qualified financial advisor for advice tailored to your situation.
Assumptions: Calculations assume a constant contribution, a constant APY when interest is enabled, deposits at the end of each period, and no fees, taxes or inflation unless you fold those into the target yourself. Priority badges do not change the math.
Estimation Purposes Only: The chart and month-by-month table are illustrative. Prices for cars, travel and home repairs move, and a high-yield rate is not guaranteed. The default 4.5% APY is a token rate for planning, not a quote from any institution.
Please email all suggestions for improvements and any bug reports to: sinkingfundsplanner@personalfinances.me, thank you.