Finance calculator
Simple interest calculator
Find interest calculated only on the original principal, without compounding.
Calculate simple interest
Enter the principal, annual rate, and time.
Principal plus interest
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Results are estimates and do not include fees or taxes.
Simple interest formula
Simple interest applies the rate to the original principal for the entire term. Previously earned interest does not earn additional interest.
Interest = principal × annual rate × time
Example
At 5% simple interest, $5,000 earns $250 per year. Over three years, the interest is $750 and the final balance is $5,750.
Simple versus compound interest
Simple interest grows by the same dollar amount each period. Compound interest recalculates returns using a growing balance, so it usually produces a different result over longer periods.
Method reviewed September 25, 2026. See our calculation methodology.