💹 Compound Interest Calculator

See how money grows with compound interest over time.

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What is a Compound Interest Calculator?

Albert Einstein reportedly called compound interest the eighth wonder of the world, and once you see the numbers, it's easy to understand why. Unlike simple interest, compound interest is calculated on your principal plus all the interest already accumulated — so your money doesn't just grow, it grows on its own growth. This calculator projects the future value of a lump sum, such as a fixed deposit or one-time investment, based on the rate and compounding frequency you choose.

Compound Interest Formula

A = P × (1 + r ÷ f)f × t

Where P is the principal, r is the annual interest rate (as a decimal), f is the compounding frequency per year (1 for annual, 4 for quarterly, 12 for monthly), and t is the time in years. Interest earned is simply A minus P.

Worked Example

Invest ₹1,00,000 at 8% per annum for 5 years, compounded annually:

A = 1,00,000 × (1.08)5 ≈ ₹1,46,933

Now compare that to the same ₹1,00,000 at 8%, compounded quarterly instead:

A = 1,00,000 × (1 + 0.08 ÷ 4)4 × 5 = 1,00,000 × (1.02)20 ≈ ₹1,48,595

Just by switching the compounding frequency from annual to quarterly, your final corpus grows by roughly ₹1,662 — with no change to your deposit or the headline interest rate. This is exactly why fixed deposits with quarterly or monthly compounding technically outperform ones compounded only annually, even when both are advertised at the same "8% p.a."

How to Use This Calculator

  1. Enter the Principal amount you're investing.
  2. Enter the Annual Interest Rate.
  3. Enter the Time Period in years.
  4. Click Calculate to see the maturity amount and total interest earned.
💡 Tip: When comparing FDs from banks like SBI, HDFC, or ICICI, always check the compounding frequency in the fine print — a slightly lower rate with monthly compounding can sometimes beat a higher rate compounded only annually.

For a fixed-deposit-specific breakdown including premature withdrawal rules, see the related FD Calculator.

📅 Last reviewed: July 2026 · Formulas verified against RBI/SEBI/IT Dept guidelines.