About the Compound Interest Calculator

Compound interest is one of the most powerful concepts in finance. Unlike simple interest, which is calculated only on the initial principal, compound interest is calculated on the principal plus all previously accumulated interest. This means your money grows exponentially over time, often referred to as "interest on interest."

This calculator uses the standard compound interest formula:

FV = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) - 1) / (r/n)]

Where P is the initial investment, r is the annual interest rate, n is the number of compounding periods per year (monthly = 12), t is the number of years, and PMT is the monthly contribution. The calculation assumes contributions are made at the end of each month.

Understanding compound interest is essential for retirement planning, investment decisions, and building long-term wealth. Even small regular contributions can grow into substantial amounts over decades thanks to compounding.