Interest Calculator
Calculate simple interest or compound interest on any principal amount, and see exactly how much interest you'll earn — or owe — over time.
How to Use the Interest Calculator
- 1Choose the “Simple Interest” or “Compound Interest” tab based on your need.
- 2Enter the principal amount, annual interest rate and time period.
- 3For compound interest, also select how often interest compounds (annually, semi-annually, quarterly or monthly).
- 4Your interest earned and total payable amount appear instantly.
Interest Formulas Used
- Simple Interest: SI = (P × R × T) ÷ 100
- Compound Interest: A = P × (1 + r/n)n×t, where r is the annual rate, n is the number of compounding periods per year, and t is time in years. Interest earned = A − P.
Worked comparison:₹1,00,000 at 8% for 5 years earns ₹40,000 in simple interest (total ₹1,40,000). The same amount compounded annually earns ₹46,933 (total ₹1,46,933) — compounding earns roughly ₹6,933 more over 5 years purely because each year's interest starts earning interest of its own.
The Rule of 72: a quick mental-math shortcut for compound growth — divide 72 by the annual interest rate to estimate how many years it takes an amount to double. At 8% annual compounding, money roughly doubles in 72 ÷ 8 = 9 years.
Compounding frequency changes the effective annual rate you actually earn: an 8% rate compounded monthly yields a higher effective annual return than the same 8% rate compounded annually, because interest is added to the principal more often.
Frequently Asked Questions
Formula and figures on this page were checked against official sources as of August 2026. See our editorial process. This tool is for informational purposes only and isn't financial, tax or medical advice.