How to Use the Compound Interest Calculator
Enter principal, annual interest rate, time period, and compounding frequency. Optionally add regular contributions. The calculator shows future value, APY, time to double, and a year-by-year breakdown table.
Compound Interest Calculator Formula
A = P × (1 + r/n)^(n×t)A= Final amountP= Principal (initial investment)r= Annual interest rate (decimal)n= Compounding frequency per yeart= Time in years
Example Calculation
₹1 lakh at 8% p.a. compounded monthly for 10 years:
A = 100000 × (1 + 0.08/12)^(12×10) = 100000 × (1.006667)^120
Future Value ≈ ₹2,21,964; Interest earned ≈ ₹1,21,964; APY ≈ 8.30%
Frequently Asked Questions
What is the compound interest formula?
A = P × (1 + r/n)^(nt), where A = final amount, P = principal, r = annual interest rate (decimal), n = compounding frequency per year, t = time in years.
What is the Rule of 72?
Divide 72 by the annual interest rate to estimate years to double your money. At 8%, your money doubles in roughly 9 years (72 ÷ 8 = 9).
What is APY vs APR?
APR is the stated annual interest rate before compounding. APY (Annual Percentage Yield) is the effective rate after compounding is applied. APY is always higher than APR when compounding occurs more than once per year.