Compound interest calculator
See how your money grows with the power of compounding over time. Supports all major currencies.
How compound interest works
Compound interest earns returns on both the original principal and the accumulated interest from previous periods. The formula is A = P × (1 + r/n)nt, where P is the principal, r is the annual interest rate (decimal), n is compounding frequency per year, and t is time in years. The final interest earned is A − P.
The compounding frequency makes a measurable difference: $10,000 at 8% for 10 years yields $21,589 compounded annually, $21,911 monthly, and $21,980 daily. More frequent compounding always produces more. A useful mental shortcut is the Rule of 72: divide 72 by the annual interest rate to estimate years to double your money — at 8%, money doubles in ~9 years; at 12%, in ~6 years. Compound interest is the core engine behind savings accounts, fixed deposits, mutual funds, and debt. Understanding it helps you choose higher-frequency compounding options and start investing as early as possible, since time is the most powerful variable.