Compound interest means you earn interest on your interest. Over long periods it's the single biggest driver of wealth. This calculator shows how a sum grows with yearly, quarterly or monthly compounding, with optional monthly additions.
The compound interest formula
A = P × (1 + r ÷ n)^(n × t)P = principal, r = yearly rate ÷ 100, n = times compounded a year, t = yearsInterest = A − PSimple interest, by contrast, is only P × r × t, earned on the original amount alone.
Worked example
Example: ₹1 lakh at 10% for 10 years
Simple interest: ₹1 lakh interest, total ₹2 lakh.
Compounded yearly: ₹2,59,374.
Compounded quarterly: ₹2,68,506.
The rule of 72
A quick way to estimate doubling time: divide 72 by the yearly rate. At 8%, money doubles in about 9 years; at 12%, in about 6. Starting even five years earlier can double your final amount, which is why time matters more than the amount you start with.
For investments that add money every month, see the SIP calculator.
How to use this calculator
- Enter the starting amount and any monthly addition.
- Enter the rate, time and how often it compounds.
FAQs
Simple vs compound interest?
Simple interest is only on the original amount; compound interest is also earned on past interest.
Results are estimates and aren't financial advice. For decisions about your own money, check with a qualified adviser. Spotted a mistake? Tell us.