See what a one-time amount becomes as compounding does its work.
A compound interest calculator shows what a one-time amount grows to over time as interest earns interest, using your rate, time horizon, and compounding frequency.
Simple interest grows in a straight line; compound interest curves upward, because each period's interest is added to the balance and earns interest itself. The effect is modest over a year or two and dramatic over decades, the reason starting early matters so much more than the rate you earn.
More frequent compounding raises the result for the same nominal rate, though the gap between monthly and daily is small compared with the effect of time. The two biggest drivers are the return and the number of years, doubling the horizon does far more than nudging the rate, which is why compounding rewards patience above all.
Future value = principal × (1 + rate ÷ n)^(n × years), where n is compounding periods per year. Interest is added to the balance and earns further interest.
Simple interest is earned only on the principal; compound interest is earned on the principal plus accumulated interest, so it grows faster over time.
More frequent compounding helps, but time and rate matter far more. The gap between monthly and daily compounding is small.
See the exact formula and a worked example on our methodology page.