How to Calculate Compound Interest and Grow Your Savings

Compound interest is one of the most powerful forces in personal finance. Unlike simple interest — which is calculated only on the principal — compound interest is calculated on the principal plus all previously accumulated interest. This means your money grows exponentially over time, not linearly.

The Compound Interest Formula

The formula for compound interest is: A = P × (1 + r/n)^(nt), where A is the final amount, P is the principal, r is the annual interest rate (decimal), n is the number of times interest compounds per year, and t is the number of years.

A Simple Example

Say you invest ₹1,00,000 at 10% annual interest, compounded annually, for 10 years. With simple interest, you would earn ₹1,00,000. With compound interest, your investment grows to ₹2,59,374 — more than 2.5x your original amount. The extra ₹59,374 comes purely from compounding.

The Power of Compounding Frequency

The more frequently interest compounds, the faster your money grows. Monthly compounding beats annual compounding, and daily compounding beats monthly. For long-term investments like FDs or mutual funds, compounding frequency makes a meaningful difference over a decade or more.

Starting Early Makes All the Difference

Time is the biggest factor in compound interest. Someone who invests ₹5,000/month starting at age 25 will retire with significantly more than someone who starts at 35 — even if the late starter invests more per month. The extra 10 years of compounding is that powerful.

Use Our Compound Interest Calculator

Try our free Compound Interest Calculator to run your own scenarios. Enter your principal, rate, compounding frequency, and time period to instantly see how your money grows year by year.