How to use the Compound Interest Calculator
- Enter a starting amount and, optionally, a monthly contribution.
- Set the annual interest rate, number of years and compounding frequency.
- Review the future value, total interest and the year-by-year table.
The compound interest formula
A = P × (1 + r/n)^(n × t)P is the initial amount, r the annual rate as a decimal, n the compounding periods per year and t the years. Compound interest (CI) is A − P. With regular contributions, each month's balance grows at the monthly rate equivalent to your chosen compounding frequency, then the contribution is added.
Why compounding frequency matters (a little)
The more often interest compounds, the higher the effective annual rate: 10% compounded yearly is 10%, but compounded monthly it is 10.47%. The difference is real but small compared with the effect of the rate itself and, above all, time.
The rule of 72
Divide 72 by the annual rate to estimate how many years it takes money to double. At 8% that's about 9 years; at 12%, about 6 years.
Example
- ₹1,00,000 at 10% compounded yearly for 10 years grows to ₹2,59,374.
- Compounded monthly instead, it grows to ₹2,70,704.
- Adding ₹5,000 every month (monthly compounding) brings the total to about ₹12.95 lakh, of which ₹7 lakh is your own money.
Frequently asked questions
What's the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is also calculated on interest already earned, so growth accelerates over time.
Can I use other currencies?
Yes. Choose a currency to change the formatting; the maths is the same in any currency.
Is what I enter stored or sent anywhere?
No. Calculations and processing happen in your browser. Nothing you type is sent to our servers. Some tools remember your last input in this browser's local storage for convenience; you can clear it at any time.