Compound Interest Calculator — Calculate CI
Calculate compound interest on any principal amount. See how investments grow with monthly, quarterly, or annual compounding.
By SwiftCalcTools Editorial Team · Formula verified
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How to Use Compound Interest Calculator
- 1Enter the required values in the input fields above.
- 2Click the Calculate button or results update instantly as you type.
- 3View your results in the output panel below the inputs.
- 4Adjust any values to recalculate instantly.
Frequently Asked Questions
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest (calculated only on principal), compound interest grows exponentially. Einstein allegedly called it "the eighth wonder of the world."
More frequent compounding yields higher returns. Example: ₹1 lakh at 10% for 1 year — Annual: ₹1,10,000. Quarterly: ₹1,10,381. Monthly: ₹1,10,471. Daily: ₹1,10,516. The difference grows significantly over longer periods. Most mutual funds and bank FDs compound quarterly in India.
The Rule of 72 is a shortcut to estimate how long it takes to double your money: divide 72 by the annual interest rate. At 10% → doubles in 7.2 years. At 12% → doubles in 6 years. At 6% → doubles in 12 years. At 72% → doubles in 1 year. It's accurate for rates between 6–12%.
EAR (also called APY — Annual Percentage Yield) accounts for compounding frequency. A 10% rate compounded monthly has an EAR of 10.47%, meaning you effectively earn 10.47% per year. Banks advertise the nominal rate; EAR shows the true annual yield. Use EAR to compare investments with different compounding frequencies.