Backwards Compound Interest Calculator
Use this backwards compound interest calculator to start with a future goal and find the initial balance required today. Add recurring deposits to separate your contributions from compound growth.
Written and checked by TheToolNet Editorial Team · Last reviewed: September 27, 2026 · Editorial method
Without deposits, present value = future value ÷ (1 + annual rate ÷ periods per year)years × periods per year.
Work backwards from your target
What the backwards calculation does
A normal compound-interest calculation grows a known principal forward. This version rearranges that process. It first calculates how much every end-of-period deposit contributes at the target date, subtracts that value from the goal, and discounts the remainder back to today.
Deposit timing matters
A deposit made at the beginning of a period earns one more period of growth than an end-of-period deposit. This tool uses end-of-period deposits, matching Excel's default type=0 convention. Use the compound interest calculation in Excel page to build a spreadsheet formula.
Worked example
For a 50,000 target in ten years at 6% compounded monthly with 100 added each month, the calculator discounts both the goal and the deposit stream. The verification line then grows the calculated starting amount forward again; small display differences are rounding.
Limits
This is a constant-rate mathematical projection. It does not predict investment returns or include tax, inflation, account fees, changing rates, missed deposits, or deposit limits. A negative result is rejected when deposits alone would exceed the chosen target.
Frequently asked questions
Can I use this for a savings goal?
Yes, if you enter a reasonable fixed rate assumption. Compare several rates rather than treating one projection as certain.
Why is daily compounding different?
The nominal annual rate is divided into more periods. The effective annual rate can therefore be slightly higher than with less frequent compounding.