📈 Compound Interest Calculator
Enter principal, interest rate, and time to see your investment grow year by year.
❓ FAQ
A = P × (1 + r/n)^(n×t) where P = principal, r = annual interest rate, n = compounding periods per year, t = time in years. For example: $10,000 × 7% × 20 years (annual) = $38,697.
Simple interest only earns interest on the principal. Compound interest earns interest on both the principal and previously accumulated interest. The longer the time horizon, the more dramatic the difference becomes.
A quick way to estimate how long it takes to double your money: divide 72 by the annual interest rate. For example, at 6% annual return, 72 ÷ 6 = 12 years to double your investment.
More frequent compounding (monthly vs. annually) produces slightly higher returns at the same nominal rate. The difference is small at low rates but becomes more significant at higher rates and over longer periods.