Interest Calculator
Calculate simple or compound interest on any principal amount.
Total after interest
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About this calculator
Simple interest is calculated only on the original principal for the entire period. Compound interest is calculated on the principal plus previously accumulated interest, so it grows faster the more frequently it compounds — this is why compound interest is used for most savings accounts and loans in practice.
What's the formula for compound interest?
A = P × (1 + r/n)^(n×t), where P is principal, r is annual rate as a decimal, n is compounding frequency per year, and t is time in years.
Why does compounding frequency matter?
The more often interest compounds — monthly instead of annually, for example — the more total interest accumulates over the same period and rate, since each compounding period earns interest on a slightly larger balance.