Compound Interest Calculator — See How Your Money Grows
See how your money grows with compound interest over time.
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How This Calculator Works
A = P(1 + r/n)^(nt) + PMT × [(1+r/12)^(12t) - 1] / (r/12)
Where A = final amount, P = principal, r = annual rate, n = compounding frequency, t = years, PMT = monthly contribution.
Frequently Asked Questions
At 7% annual return: $10,000 grows to ~$19,672. At 10%: ~$25,937. Daily compounding adds a few percentage points over annual compounding.
Daily compounding earns slightly more. $10,000 at 7% daily vs monthly for 30 years: daily earns ~$87 more. Compounding frequency matters less than rate.
Adding $500/month at 7% for 30 years grows to ~$589,000. The same money without contributions only grows to ~$76,000. Contributions amplify compounding dramatically.
Divide 72 by your interest rate to find doubling time. At 6%, money doubles in 12 years. At 9%, it doubles in 8 years.
Use 7% for diversified stock index funds (historical real return). 4-5% for bonds or CDs. 10% for nominal S&P 500 before inflation.
Always, for long-term investing. Compound interest earns interest on interest. Simple interest only earns on principal. The difference is massive over decades.
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Calculations are for educational purposes only. Consult a qualified financial advisor for personalized advice.