Compound Interest Calculator
Project how a starting balance and regular monthly contributions grow over time with compounding interest.
Why compounding frequency changes the outcome
The formula behind this tool, A = P(1 + r/n)nt, means interest earned also earns interest — and how often that happens (annually vs. monthly vs. daily) meaningfully changes the total over long time horizons, even at the same stated rate.
A common misreading
The "Rule of 72" (72 ÷ rate ≈ years to double) is a handy mental shortcut, not an exact answer — real doubling time depends on the precise rate and compounding frequency, which is exactly what this calculator computes directly instead of approximating.