Compound Interest Calculator
See how your balance grows with compound interest and compare compounding frequencies.
Compound interest means you earn returns on both your original balance and on interest that has already been credited. Over time, growth accelerates because the base amount that earns the next period's interest is larger. This calculator uses a nominal annual rate (the stated APR) and applies it according to the compounding frequency you choose.
Simple interest would pay interest only on the starting principal each year. Compound interest reinvests interest, so the same quoted rate produces a higher ending balance when compounding happens more often (monthly vs annually, for example). In the limit of infinitely frequent compounding, balance grows by the continuous formula P·e^(r·t), which is why the "Continuous" option slightly exceeds daily for the same nominal rate.
Here P is principal, r is the annual rate in decimal form, n is compounding periods per year, and t is time in years. The effective annual yield (APY) shown in the results is the constant annual rate that would reach the same ending balance from your starting principal over your time horizon—it is always at least as large as the nominal rate when compounding happens more than once per year (and equal to it when compounding is annual).
This is an educational projection only: it does not include taxes, fees, inflation, or new contributions. Real investment returns vary and are not guaranteed. Use the shareable URL to save a scenario or compare frequencies side by side.