How does compounding frequency affect returns?

More frequent compounding produces slightly higher returns. For example, $10,000 at 7% for 10 years yields $19,672 annually, $20,097 monthly, and $20,138 continuously. The difference is most significant at higher interest rates and longer time periods.

What is the Rule of 72?

The Rule of 72 is a quick way to estimate how long it takes to double your money. Divide 72 by your annual interest rate: at 7%, your money doubles in approximately 72/7 = 10.3 years. At 10%, it doubles in about 7.2 years.

Should I contribute at the beginning or end of the month?

Contributing at the beginning of each month earns slightly more because each contribution has an extra month to compound. The difference is small but adds up over decades. If you have the choice, beginning-of-month contributions are mathematically better.

Why adjust for inflation?

Inflation reduces the purchasing power of future money. A balance of $100,000 in 30 years won't buy what $100,000 buys today. Adjusting for inflation (typically 2-3%) shows the 'real' value of your investment in today's dollars, giving a more realistic picture of future wealth.

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Compound Interest Calculator

Calculate compound interest with monthly contributions. Compare compounding frequencies, adjust for inflation, and track growth on an interactive chart.

Last updated: March 31, 2026

Initial Investment

Annual Interest Rate

Time Period

years

Monthly Contribution

Compounding Frequency

Contribution Timing

Adjust for inflation

Disclaimer: This calculator provides estimates for educational purposes only. It does not constitute financial advice. Actual investment returns vary based on market conditions, fees, and other factors. Consult a qualified financial advisor for investment decisions.

How to Use This Calculator

Enter your initial investment amount.
Set the annual interest rate and compounding frequency.
Add monthly contributions if applicable.
Optionally enable inflation adjustment to see real purchasing power.
View the live chart showing your balance growth over time.

The Formula

A = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)]. Where: P = principal, r = annual rate, n = compounding frequency, t = years, PMT = periodic contribution. Continuous: A = Pe^(rt).

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Frequently Asked Questions

Compound interest is interest earned on both the original principal and on previously accumulated interest. Unlike simple interest (which only earns on the principal), compound interest accelerates growth over time — the longer your money compounds, the faster it grows.

Methodology & Sources

Growth calculated using the compound interest formula A = P(1 + r/n)^(nt) with optional periodic contributions. Inflation adjustment uses real rate of return.