Compound Interest Calculator
Compute compound interest with optional monthly contributions — all in your browser.
How the compound interest calculator works
Compound interest means the interest you earn also earns interest in subsequent periods. Enter a starting principal, annual rate, investment horizon, and how frequently interest compounds (annually, quarterly, monthly, or daily). An optional monthly contribution adds regular deposits to the calculation, modelling a savings or investment account with recurring top-ups.
The future value figure is the projected balance at the end of the term. Total contributed is your out-of-pocket cost (principal plus all monthly additions). Interest earned is the difference — the growth generated by compounding alone. Even modest rates produce meaningful gains over long horizons, which is the central insight behind long-term investing.
FAQ
What compounding frequency should I choose? Use whatever your account or investment specifies. Most savings accounts and bonds compound monthly or daily; some bonds compound semi-annually.
Does this account for inflation? No. The result is a nominal future value. To estimate real purchasing power, subtract the expected inflation rate from the annual rate before entering it.
Is my data sent anywhere? No. All calculations happen locally in your browser.
This tool is for reference only and does not constitute financial advice.