How is this different from a stock return calculator?

This calculator uses a fixed interest rate. The Stock Return Calculator on Custom Stock Alerts uses real historical prices, dividends, stock splits, and optional DRIP for specific tickers.

What is the Rule of 72?

Divide 72 by your annual interest rate to estimate how many years it takes to double your money at that rate.

Compound Interest Calculator

See how your money grows with compound interest and optional monthly contributions. Enter an initial deposit, contribution amount, interest rate, and time horizon, then view your ending balance, interest earned, year-by-year schedule, and chart.

Note: This tool uses a constant annual rate for illustration. Real investments (stocks, ETFs, dividends) vary. For historical returns on real tickers with DRIP, use our Stock Return Calculator.

Calculator inputs

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Model actual tickers with dividends, splits, and periodic investments, not just a fixed rate.

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Future balance

Total contributions

Total interest earned

Effective annual yield (APY): -

Rule of 72 (approx. double): -

Exact time to double: -

Where your balance comes from

■ Initial - ■ Added contributions - ■ Interest -

Year-by-year growth

Year	End balance	Total contributed	Interest earned

What is compound interest?

Compound interest means you earn interest on your balance and on interest already earned. Over long horizons, that snowball effect dominates growth, especially when you add regular contributions.

The future value with monthly contributions (end of month) is often written as:

FV = P(1 + r/n)^nt + PMT × [((1 + r/n)^nt − 1) / (r/n)]

Where P is initial principal, PMT is the periodic contribution, r is the annual rate, n is compounding periods per year, and t is years.

Frequently asked questions

This page uses a fixed interest rate. Our Stock Return Calculator uses real historical prices, dividends, stock splits, and optional DRIP for specific tickers.

Yes. Contributions at the beginning of each period earn slightly more interest than at the end. Use the contribution timing dropdown to compare.

Divide 72 by your annual rate to estimate years to double your money (e.g. 7% → about 10 years). It is a shortcut; we also show the exact doubling time from the rate you enter.

Yes. Create a free account for ex-dividend and price alerts, or explore all features.

Disclaimer: Results are hypothetical and do not reflect taxes, fees, or market risk. Rates shown on presets (e.g. savings APY or long-term stock averages) are for education only, not investment advice.