Compound Interest Calculator
See how your savings or investments grow with compound interest over any time period. Works for savings accounts, fixed deposits, mutual funds, and any compound growth scenario.
Compound interest
The power of compound interest
Compound interest means you earn interest on your interest, not just the original principal. A $10,000 investment at 7% annual return becomes $19,672 after 10 years and $76,123 after 30 years — without adding another dollar.
Formula: A = P × (1 + r)^t. Where A = final amount, P = principal, r = annual rate (as decimal), t = years.
Frequently asked questions
Simple interest = Principal × rate × time. Compound interest reinvests the earnings each period. At 10% for 10 years: simple interest = 100% gain; compound interest = 159% gain.
Frequency varies by product. Savings accounts: daily or monthly. Fixed deposits: quarterly. Mutual funds: effectively daily. More frequent compounding gives slightly higher returns.
Divide 72 by the annual interest rate to estimate how many years to double your money. At 7% p.a.: 72 ÷ 7 ≈ 10.3 years to double. At 10%: about 7.2 years.