Sinking Fund Calculator
Results are estimates based on the values you enter. Recheck your inputs and assumptions before using the output for decisions.
Calculate the periodic deposit needed to reach a sinking fund target amount.
Sinking Fund Calculator
Free online sinking fund calculator to estimate the periodic deposit needed to reach a future target amount. This calculator is useful for savers, business owners, accountants, finance students, homeowners, and anyone planning ahead for a known future expense such as equipment replacement, debt repayment, tuition funding, property repairs, or a large purchase. A sinking fund is a pool of money built gradually over time through regular deposits plus interest earnings. Instead of waiting for a large bill to arrive, a sinking fund helps spread the cost across many smaller contributions.
This calculator uses four main inputs. Target amount means the future fund balance you want to reach. Annual interest rate means the interest earned on the sinking fund balance. Years means the time available to build the fund. Deposits per year means how often deposits are made, such as annually, quarterly, monthly, biweekly, or weekly. Once those values are entered, the calculator shows required deposit per period, required annual contribution, total contributions, and interest earned. These results help you see how much of the target comes from your own deposits and how much comes from growth.
The formula of sinking fund
Periodic rate = Annual interest rate / Deposits per year
Total periods = Years x Deposits per year
Required deposit per period = Target amount x Periodic rate / [(1 + Periodic rate)^Total periods – 1]
Total contributions = Required deposit per period x Total periods
Interest earned = Target amount – Total contributions
Here target amount means the future balance you want to accumulate, periodic rate means the rate earned each deposit period, total periods means the number of deposits made over the full saving timeline, required deposit per period means the recurring amount you must contribute each period, total contributions means the sum of all deposits made by you, and interest earned means the part of the target produced by investment growth rather than deposits.
Solved Example
Example 1: Find the required monthly sinking fund deposit for a $50,000 target in 10 years at 6% annual interest.
Solve: Periodic rate = 6% / 12 = 0.5% per month
Total periods = 10 x 12 = 120
Required deposit per month = 50000 x 0.005 / [(1.005)^120 – 1] = $303.03
Required annual contribution = 303.03 x 12 = $3,636.36
Total contributions = 303.03 x 120 = $36,363.60
Interest earned = 50000 – 36363.60 = $13,636.40
Example 2: Find the result for a $20,000 target in 5 years at 4% with quarterly deposits.
Solve: Periodic rate = 4% / 4 = 1% per quarter
Total periods = 5 x 4 = 20
Required deposit per quarter = 20000 x 0.01 / [(1.01)^20 – 1] = $905.41
Total contributions = 905.41 x 20 = $18,108.20
Interest earned = 20000 – 18108.20 = $1,891.80
Example 3: Find the result for a $12,000 target in 3 years at 0% with annual deposits.
Solve: With zero interest, required deposit = 12000 / 3 = $4,000 per year
Total contributions = $12,000
Interest earned = $0
Table of sinking fund calculator
| Target Amount | Years | Interest Rate | Required Deposit per Period |
|---|---|---|---|
| $12,000 | 3 | 0% | $4,000.00 |
| $20,000 | 5 | 4% | $905.41 |
| $50,000 | 10 | 6% | $303.03 |
| $100,000 | 15 | 5% | $367.69 |
How to use this sinking fund calculator
Enter the target amount in the proper input field. After that, enter the annual interest rate, the number of years, and how many deposits will be made per year. Then click the calculate button. The calculator will show the required deposit per period, required annual contribution, total contributions, and interest earned in the result box.
This calculator is especially useful when you know the future amount needed but want to save toward it gradually. It helps translate a large goal into a manageable recurring contribution. That makes it practical for maintenance reserves, tuition plans, vacation funds, vehicle replacement funds, and debt-repayment reserves. It also makes it easier to compare how different interest rates or deposit frequencies change the amount you must set aside.
When using the result, remember that this calculator assumes deposits are made consistently and that the interest rate remains constant throughout the full period. Real-world savings accounts and investment returns may change over time. Even so, a sinking fund remains one of the most practical ways to plan for a known future cost, and this calculator gives a quick way to estimate the recurring contributions required to reach that goal.