Compound interest calculator help

The Compound Interest Calculator projects a balance from a starting amount, recurring contributions, a rate, a time horizon, and a compounding frequency, entirely in your browser.

Rate Inputs

The rate field accepts either a nominal annual rate or an APY, controlled by the rate mode toggle. APY inputs are converted to the equivalent nominal annual rate for the selected compounding frequency before the projection runs, so both modes describe the same growth once frequency is accounted for.

Compounding Frequencies

Supported frequencies are annual, semiannual, quarterly, monthly, daily, and continuous. Continuous compounding uses exponential growth. The result panel also reports the effective annual yield so you can compare settings on equal footing.

Contributions And Timing

Contributions can be weekly, biweekly, monthly, quarterly, or annual, and are treated as evenly spaced. Beginning timing adds each contribution at the start of its period, including time zero; end timing adds it at the end. Beginning contributions earn slightly more because they spend longer invested.

What The Result Shows

The projection reports the final balance, total contributed, interest earned, growth multiple, and a year-by-year schedule splitting each year into starting balance, contributions, and interest.

Limitations

The calculator does not include taxes, fees, inflation, live rates, or rate changes over time, and it does not connect to any account. It is an educational projection of the assumptions you enter, not financial advice.

Related Calculators

Convert between rates and yields with the APY calculator, add fee and inflation assumptions with the investment calculator, or test a full drawdown plan with the retirement calculator.

FAQ

Should I enter a nominal rate or an APY?

Either works. Use the nominal rate mode for a stated rate before compounding. Use the APY toggle when your bank or example quotes an annual percentage yield; the calculator converts it to an equivalent nominal rate for the selected compounding frequency before projecting.

What does contribution timing (beginning vs end) change?

Beginning contributions are added at the start of each contribution period, including time zero, so they earn interest for that period. End contributions are added at the end of each period. The difference grows with larger deposits, higher rates, and longer horizons.

Does the calculator include taxes, fees, or inflation?

No. The projection uses only the rate, contributions, and time you enter. It does not subtract taxes or fees, adjust for inflation, or use live rates. Use the investment calculator when fee drag and inflation should be part of the result.

How is continuous compounding handled?

Selecting continuous compounding applies exponential growth using e raised to the rate, the mathematical limit of compounding more and more often. It produces a slightly higher result than daily compounding at the same nominal rate.