Enter principal, annual rate, and investment years to calculate compound interest returns. Supports monthly contribution mode with visual growth charts.
Lump Sum: FV = PV x (1 + r/n)^(n x t)
Monthly Contributions: FV = PV x (1 + r/n)^(n x t) + PMT x [((1 + r/n)^(n x t) - 1) / (r/n)]
Where PV = initial principal, PMT = monthly contribution, r = annual rate, n = compounding frequency per year, t = years
Rule of 72: Doubling time (years) = 72 / Annual Rate (%)