Calculate simple interest or compound interest on any savings, investment or loan. See exactly how your money grows over time with annual, monthly or daily compounding. Free, fast and accurate — used by savers and investors worldwide.
Toggle between simple and compound interest to compare investment growth
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The key difference is that simple interest is calculated only on the original principal, while compound interest is calculated on the principal plus all previously earned interest — meaning your interest earns interest.
A = P × (1 + r × t) — where P = principal, r = annual rate, t = time in years.
Example: 0,000 at 5% for 5 years = 0,000 × (1 + 0.05 × 5) = 2,500
A = P × (1 + r/n)^(n×t) — where n = compounding frequency per year.
Example: 0,000 at 7% compounded monthly for 10 years = 0,097 — more than doubling the investment!
Albert Einstein reportedly called compound interest the "eighth wonder of the world." The reason is dramatic long-term growth. 0,000 invested at 7% for 30 years grows to over 6,000 with compound interest versus just 1,000 with simple interest. Starting early makes an enormous difference.
Whether you are saving in a bank account, fixed deposit, ISA (UK), superannuation (Australia), 401(k) (USA), PPF (India) or any other investment vehicle, compound interest works the same way everywhere. This free calculator shows you exactly how your money grows over time.
The more frequently interest is compounded, the more you earn. Daily compounding gives slightly more than monthly, which gives more than annual. Many savings accounts and fixed deposits compound interest monthly or annually — check with your bank or financial institution to find your compounding frequency.
This calculator also works in reverse — you can use it to understand how interest accumulates on a personal loan, student loan, car loan or credit card balance. Enter the loan amount as your principal, your interest rate and the loan term to see the total interest cost over time.