Sinking Fund Contribution CalculatorFree online financial calculator — instant results, no sign-up
Divide a future expense among the remaining deposits without assuming interest.
Estimates only, based on the inputs and assumptions shown. This is not financial, investment, tax, or legal advice. Prices, rates and local rules may change; crypto scenarios do not predict returns. Confirm important decisions with a qualified professional.
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About the Sinking Fund Contribution Calculator
The Sinking Fund Contribution Calculator divides an upcoming expense across the deposits you still plan to make, after subtracting money already reserved. It assumes no interest, so the result is the equal contribution needed per deposit to cover the remaining cost. With a $3,600 future expense, $600 already reserved, and 10 remaining deposits, the required amount per deposit is $300.00.
- Future expense ($)
- The total expected cost of the upcoming expense, in dollars; the default is $3,600.
- Already reserved ($)
- The money already set aside specifically for this expense, in dollars; the default is $600.
- Remaining deposits (deposits)
- The number of contributions you plan to make before paying the expense, measured in deposits; the default is 10.
Formula and method
C = (F − R) / N
- CRequired amount per deposit, in dollars.
- FTotal future expense, in dollars.
- RAmount already reserved for the expense, in dollars.
- NNumber of remaining deposits.
Subtract the amount already reserved from the future expense, then divide the balance by the number of remaining deposits. Using the defaults, $3,600 − $600 = $3,000 still needed, and $3,000 ÷ 10 = $300.00 per deposit. No interest or investment growth is included.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- Future expense3600 $
- Already reserved600 $
- Remaining deposits10 deposits
Results
- Amount per deposit$300.00
How to use the Sinking Fund Contribution Calculator
- 1Enter the total expected future expense; the default is $3,600.
- 2Enter the amount already reserved for this expense; the default is $600.
- 3Count the deposits you can make before payment is due and enter that count; the default is 10.
- 4Read the Amount per deposit result: the default inputs produce $300.00.
- 5Plan to set aside that amount on each remaining deposit date, and recalculate if the expense, reserved balance, or deposit count changes.
Reading your result
The Amount per deposit row shows the equal dollar contribution needed for each remaining deposit, not a monthly amount unless you plan to deposit monthly. For the default inputs, $300.00 deposited 10 times adds $3,000 to the $600 already reserved, covering the $3,600 expense.
Limitations
The calculation assumes equal deposits, no interest, no fees, no withdrawals, and an unchanged future expense. It does not account for inflation or check whether the contribution fits your budget. Enter nonnegative dollar amounts and a positive whole-number deposit count; zero deposits makes the division undefined. If the reserved amount equals or exceeds the expense, no additional saving is needed; a negative formula result represents a surplus rather than a required negative contribution. Results displayed to cents may require a small final-deposit adjustment to cover rounding.
Common questions
Should I enter the full expense or only the amount I still need to save?+
Enter the full expense in Future expense and your existing savings in Already reserved. With the defaults, enter $3,600 and $600 separately; the calculator subtracts the $600 itself.
Does Remaining deposits mean months until the expense is due?+
Only if you plan one deposit per month. Otherwise, count the actual contributions you will make before payment is due. The default count of 10 means 10 deposits, regardless of their frequency.
Does the $300.00 contribution include interest earned on the reserved money?+
No. The default result funds the entire $3,000 shortfall through 10 deposits without assuming interest. If interest is later credited and reserved for this expense, update Already reserved and the remaining deposit count.
What should I update after making a sinking fund deposit?+
Add the completed contribution to Already reserved and reduce Remaining deposits by one. Keep Future expense as the total expected cost, unless that cost has changed.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
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Results are estimates for informational purposes and are not financial, medical or legal advice.