Sinking Fund Calculator
Work out how much to set aside on each payday so a planned expense is fully funded on time. Enter your goal, your deadline, and any head start, then press Calculate.
Written by TopicDrill Editorial Team·Updated June 2026
Balance building toward your goal
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How the sinking fund calculator works
A sinking fund flips a normal savings question around. Instead of asking what a deposit will grow into, it asks what deposit is needed to land on an exact target by a set date. The tool grows any money you have already saved up to the deadline, figures out the shortfall, then solves the annuity formula for the level payment that fills it.
The chart traces two lines. The shaded area is your account balance climbing toward the goal, and the dashed line is the cash you have personally put in. The gap between them is the interest the account adds, which is why a higher rate means a smaller deposit.
A quick example
Say you want $20,000 for a car in three years, you already have $2,000, and your savings account pays 4 percent. With monthly deposits, the calculator solves for about $470 a month. Your existing $2,000 grows on its own, and interest across the 36 months shaves a little off what you would otherwise have to deposit.
Things to keep in mind
Keep the fund in an account you will not dip into, and revisit the numbers if the price of your goal changes. For a primer on saving toward goals from a neutral source, see the CFPB guidance on building a budget. If your goal is open-ended rather than fixed, our savings goal calculator may fit better.
Frequently asked questions
What is a sinking fund?
A sinking fund is money you set aside on a schedule so a known expense is fully paid for by the time it arrives. Instead of borrowing or scrambling when the bill is due, you spread the cost into small, predictable deposits and let any interest help close the gap.
How is the required deposit calculated?
The tool first grows your existing balance forward to the target date, subtracts that from your goal to find what the deposits must supply, and then divides by the annuity factor, which is the quantity one plus the periodic rate raised to the number of periods, minus one, divided by the periodic rate.
How is a sinking fund different from an emergency fund?
A sinking fund targets a specific, expected cost with a known amount and date, such as a new roof or annual insurance. An emergency fund is a general cushion for surprises with no fixed amount or deadline. Many people keep both, in separate accounts, at the same time.
Should I count interest on the fund?
If you park the money in a high-yield savings account or money market fund, yes. Entering a realistic rate lowers the deposit you need because the account does part of the work. If you keep the cash in a no-interest checking account, set the rate to zero.
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