See how your money grows with compound interest over time, including regular contributions.
Enter values and click Calculate to see results
Future value = P(1 + r/n)^(nt) for the initial sum, plus the annuity formula PMT x ((1 + monthly rate)^(12t) - 1) / monthly rate for monthly contributions.
Earning interest on your interest. $10,000 at 7% becomes $1,070 in year one, then earns 7% on $10,700 in year two — the growth accelerates every year without you adding a cent.
Over a 20-year horizon, monthly contributions typically produce most of the final balance, with the initial sum a smaller share. Starting early and contributing steadily beats waiting for a bigger lump sum.