Calculate Interest — and See What the Rate Means in Real Money

Where:

• A = Final amount (what your money grows to)
• P = Principal (your initial deposit)
• r = Annual interest rate (as a decimal, e.g. 7% = 0.07)
• n = Number of times interest is compounded per year (e.g. 12 for monthly)
• t = Number of years

For example, $1,000 at 7% interest compounded monthly for 10 years becomes $2,009.66. Add $200/month and the final amount jumps to $36,559 — that's the power of consistent contributions combined with compound interest.

Don't want to do the math by hand? Our free compound interest calculator does it instantly.

The real magic of compound interest happens over long time horizons. A small difference in interest rate or contribution amount can lead to tens of thousands of dollars in extra wealth.

• $200/month at 7% for 30 years → approximately $243,000 (you only contributed $72,000)
• Starting 10 years earlier can more than double your final balance
• Increasing contributions by just $50/month can add $40,000+ over 20 years

Small changes lead to massive results — and the earlier you start, the more compound interest works in your favor. Use our investment growth calculator to model different scenarios.

Follow these simple steps using our free calculator:

1. Enter your starting amount — how much money you have now (e.g. $1,000)
2. Add a monthly contribution — how much you plan to save each month (e.g. $200)
3. Set the interest rate — the expected annual return (e.g. 7% for stock market average)
4. Choose the time period — how many years you plan to save or invest
5. See your results instantly — final amount, total contributions, and interest earned

All calculations happen instantly in your browser. No data is stored, and no signup is required. Try different values to see how adjustments affect your future balance.