Calculate simple or compound interest on any principal amount.
Simple interest is calculated only on the original principal for the entire period. Compound interest is calculated on the principal plus any interest already added, so it grows faster the longer money sits and the more often it compounds.
Simple interest is Principal × Rate × Time, divided by 100. For example, 10,000 at 7% for 3 years is (10,000 × 7 × 3) ÷ 100 = 2,100.
Compound interest uses the formula A = P × (1 + r/n)^(n×t), where P is the principal, r is the annual rate, n is how many times it compounds per year, and t is time in years. The interest earned is A minus the original principal.
More frequent compounding means interest is added to the balance more often, so each new interest calculation is based on a slightly larger amount. Monthly compounding earns more than annual compounding at the same stated rate, even though the difference is often small.