📈 Compound Interest Calculator

How the Compound Interest Calculator Works

This compound interest calculator shows how an investment or savings balance grows over time when the interest you earn is added back to the principal, so future interest is earned on a larger and larger amount. That snowball effect is what separates compound growth from simple interest, where you only ever earn a return on your original deposit.

To use it, enter your starting principal, the annual interest rate, the number of years you plan to keep the money invested, and how often interest compounds (yearly, quarterly, monthly, or daily). If you add regular contributions, the tool folds those into each period as well, giving you a realistic projection of the final balance and the total interest earned.

Why Compounding Matters

The longer your time horizon, the more powerful compounding becomes, because each cycle builds on every cycle before it. Even a modest rate can produce a striking difference over several decades. Use the results to compare scenarios, set savings goals, or understand how compounding frequency changes your annual yield. Figures here are estimates for planning only and assume a constant rate; actual returns vary, so treat them as a guide rather than a guarantee.