Compound interest calculator with monthly contributions
Enter a starting balance, a monthly contribution, and an interest rate — the calculator shows you the final amount and how much of it is interest earned, not money you put in.
Contributed Interest
How compound interest with monthly contributions is calculated
Compound interest capitalizes every month: each contribution starts earning its own interest the moment it goes in, not just the starting balance. That's why the curve accelerates over time instead of growing in a straight line — the longer you let it run, the bigger the share that comes from interest earned rather than money you put in. This calculator compounds monthly: each month it adds interest on the current balance, then adds your contribution.
⚠ Tool for educational and informational purposes only — not investment advice or a recommendation to buy or sell. Investing carries risk of capital loss. Read the full disclaimer.