Use this free online interest rate calculator to find the annual interest rate needed to grow a principal amount into a target final amount over a given time period, using either simple or annually compounded interest.
How to Use the Interest Rate Calculator
Enter the starting amount in the "Principal (₹)" field.
Enter the amount you expect to end up with in "Final / Maturity Amount (₹)".
Enter the duration in "Time (years)".
Choose "Simple Interest" or "Compound Interest (Annual)" from "Interest Type".
Click "Calculate Rate" to view the required annual interest rate.
Frequently Asked Questions
For "Simple Interest", the rate is solved from Rate = ((Final Amount − Principal) × 100) ÷ (Principal × Time). For "Compound Interest (Annual)", the rate is solved from Rate = ((Final Amount ÷ Principal)^(1/Time) − 1) × 100, which accounts for annual compounding.
The calculator solves for a positive growth rate, so the "Final / Maturity Amount" must be entered as a value greater than the "Principal". If it isn't, or if any field is missing or zero, the calculator shows "Invalid input!" instead of a rate.
Yes. If you know how much you invested (or borrowed), what it grew to (or how much you repaid), and over how many years, this calculator backs out the annual interest rate that produced that result, for either simple or annually compounded interest.
Yes, it's completely free, requires no registration, and you can run as many calculations as you need.