CompoundLab

Compound Interest Calculator

A free compound interest calculator that projects how a starting balance grows over time at a fixed annual rate. It applies the exact compound formula P*(1+r/n)^(n*t) to your principal, then layers on an optional recurring monthly contribution grown month by month, and breaks the ending balance into total contributions versus interest earned. Everything runs in your browser. The result is an estimate that assumes a constant rate and ignores taxes, fees, and inflation — not investment, tax, or financial advice.