Interest Calculator
Calculate simple or compound interest on savings or a loan. Free, instant.
Final Amount
₹1,41,477.82
₹1,00,000
Principal
₹41,477.82
Interest Earned
Interest can be calculated two fundamentally different ways. Simple interest is calculated only on the original principal for the entire duration, growing at a constant rate each year. Compound interest is calculated on the principal plus any interest already earned, which means it compounds — growing faster the longer money is left in place, since each period's interest is added to the base before the next period's interest is calculated.
This calculator handles both. Simple interest uses the straightforward formula I = P × R × T ÷ 100. Compound interest uses A = P × (1 + r/n)^(n×t), where n is how many times per year the interest compounds — annually, semi-annually, quarterly, or monthly — since the compounding frequency itself changes the final result even at the same stated annual rate.
Everything calculates instantly in your browser as you type, with no data sent anywhere. It works equally well for estimating how a savings deposit will grow or understanding how a loan's interest accumulates.
Step-by-step instructions
- 1
Choose Simple or Compound Interest
Simple interest for a flat, non-compounding calculation. Compound interest for interest that builds on itself over time.
- 2
Enter the principal amount
The starting amount being invested or borrowed.
- 3
Enter the annual interest rate and time period
The rate as a percentage per year, and the duration in years.
- 4
For compound interest, choose a compounding frequency
Annually, semi-annually, quarterly, or monthly — this affects the final amount even at the same stated rate.
- 5
Read the results
See the final amount and the total interest earned or paid.
Common use cases
Estimating how a savings deposit will grow
See how much a fixed deposit or recurring savings account could earn over time at a given rate.
Understanding a loan's interest cost
Get a sense of how much interest accumulates on a simple-interest loan over its term.
Comparing compounding frequencies
See how monthly compounding produces a different final amount than annual compounding at the same stated rate.
Financial planning and goal setting
Estimate how long it might take an investment to reach a target amount at a given rate.
Tips for best results
- More frequent compounding (monthly vs annually) produces a higher final amount at the same stated annual rate — the difference grows more noticeable over longer time periods.
- Simple interest calculations are common for certain personal loans, while savings accounts and fixed deposits typically use compound interest — check which applies to your specific product.
- For quick comparisons, try the same principal and rate under both modes to see how much of a difference compounding makes over your specific time period.
Frequently asked questions
What's the difference between simple and compound interest?
Simple interest is calculated only on the original principal throughout the term. Compound interest is calculated on the principal plus previously earned interest, so it grows faster over time.
Does compounding frequency really make a difference?
Yes — at the same stated annual rate, monthly compounding produces a higher final amount than annual compounding, because interest is calculated and added to the principal more often.
Which type of interest applies to my savings account?
Most savings accounts and fixed deposits use compound interest, but the exact terms vary by bank and product — check your specific account's terms to confirm.
Is my financial data stored anywhere?
No — every calculation happens locally in your browser. Nothing you enter is sent to a server or saved.
Can I use this for calculating loan interest?
Yes, for loans that use simple or standard compound interest. Loans repaid via EMI use a different reducing-balance formula — use the EMI Calculator for those instead.