Compound Interest
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Calculate growth with monthly compounding interest.
Compound interest earns interest on interest — the more frequently it compounds, the faster the balance grows.
A = P × (1 + r/n)^(n×t)
Simple interest only applies to the original principal; compound interest applies to principal plus previously earned interest, so growth accelerates over time.
More frequent compounding produces slightly higher returns for the same stated rate, though the difference is usually small compared to the impact of the rate itself.
A quick mental estimate — divide 72 by your interest rate to approximate how many years it takes an investment to double. It's a handy rule of thumb, not built into this calculator.