Compound Interest Calculator
Estimate how a starting balance and recurring contributions may grow.
All values and rates are entered by you. No live rate is assumed.
Your result
Enter your assumptions, then calculate.
Formula and method
Uses monthly compounding: balance is grown by annual rate ÷ 12 and the contribution is added each month.
Worked example
The pre-filled values demonstrate the calculation only. Change every field to match the scenario you want to explore.
Limitations
Rates and returns are user assumptions, not predictions. Fees, taxes, inflation and irregular returns can materially change outcomes.
Results exclude terms not entered, may differ because of rounding and should be checked against formal provider disclosures.
Practical next steps
- Run more than one rate or time scenario.
- Record fees and terms the calculator does not include.
- Compare the output with the provider’s written disclosure.
SmartMoney — A REVTEK publication · Reviewed 2026-09-23 · Educational information only · Methodology