Compound interest calculator
Grow a starting amount with regular contributions, with a year-by-year table and the result in today's dollars.
Assumes a steady rate, contributions at the end of each month and no tax or fees. Real returns vary and can be negative. Not financial advice.
How this calculator works
Each month the balance grows by the monthly rate, then your contribution is added: balance = balance × (1 + monthly rate) + contribution. The monthly rate comes from the annual rate and the compounding frequency: (1 + rate ÷ f)f ÷ 12 − 1. Dividing the final balance by (1 + inflation)years shows it in today's money.
Worked example: $10,000 plus $500 a month at 6% (compounded monthly) for 20 years grows to $264,122. You put in $130,000, so $134,122 is interest. At 2.5% inflation that balance is worth about $161,186 in today's dollars. Compounding more often helps only a little: $10,000 for 20 years at 6% becomes $33,198 compounded daily and $32,071 compounded yearly.
Sources and checks
You can cross-check results with:
Results can differ slightly from other tools because of rounding, fees and the assumptions each one makes.
Standard compound interest formula with regular contributions.
Figures last checked: 29 October 2026. Spotted a mistake? Tell us.