About Interest Calculator
Calculate both simple and compound interest on a principal amount. Compare how much more you earn (or owe) with compounding over the same period.
How to Use
- Enter the principal amount.
- Enter the annual interest rate and the time period.
- Choose simple or compound interest (and the compounding frequency).
- See the interest earned and the final amount.
Why Use This Tool?
- Accurate — built on precise, well-tested mathematical formulas.
- Instant — all calculations happen client-side for zero latency.
- Private — no data is sent to any server; your information stays on your device.
- Free — no sign-up, no limits, no hidden costs.
Frequently Asked Questions
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal (I = P × r × t). Compound interest is calculated on the principal plus previously earned interest, so it grows faster over time.
What is the compound interest formula?
A = P × (1 + r/n)^(n×t), where P is the principal, r the annual rate (as a decimal), n the compounding periods per year, and t the time in years. Interest earned = A − P.
Which is better for a loan — simple or compound interest?
For a borrower, simple interest is cheaper because it never charges interest on interest. Most long-term loans and deposits, however, use compound interest.
How much interest will I earn on ₹50,000 at 5%?
Simple interest on ₹50,000 at 5% per year is ₹50,000 × 0.05 = ₹2,500 a year (₹208 a month). Over 3 years that is ₹7,500. With annual compounding it would grow slightly more, to about ₹57,881 — ₹7,881 interest.
How much is 7% interest on 1 lakh?
Simple interest on ₹1,00,000 at 7% per year is ₹7,000 a year (about ₹583 a month). Enter your own principal, rate and period above to get the exact simple and compound figures.