PLANNING / FREE TOOL
Compound interest calculator
Explore compound interest and investment growth with monthly contributions. Enter your own return assumption, starting balance and savings period.
YOUR SCENARIO
Monthly compounding and end-of-month contributions. Constant hypothetical return; fees, taxes and inflation are excluded. This is a scenario, not a forecast.
How it works
Monthly rate = annual rate ÷ 12. Each month: balance = balance × (1 + monthly rate) + contribution.
Worked example
Start with 1,000, add 100 at the end of each month and assume an 8% nominal annual return compounded monthly for 10 years. The hypothetical balance is about 20,514.24, including 13,000 in contributions. This is an illustration, not a forecast.
Common questions
How are monthly contributions calculated?
The calculator applies one month of growth to the existing balance, then adds your contribution at the end of that month. It repeats this for the number of years entered.
Does the interest rate mean APR or APY?
Enter a nominal annual rate. The monthly rate is that figure divided by 12. An effective annual rate or APY is not interchangeable with that input.
Does this guarantee an investment return?
No. The return is a constant assumption you choose. Actual market returns vary, and fees, tax and inflation are excluded.
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