Simple Interest Calculator
100% PrivateCalculatorsCalculate simple interest on a principal with the textbook I = P x r x t formula.
Runs entirely in your browser. Your input is not uploaded to Ovatly or anywhere else.
Formula: interest = principal x rate x time / 100. Simple interest is paid only on the original principal, never on past interest.
- 1Enter the principal (the starting amount).
- 2Enter the annual interest rate in percent.
- 3Enter the time in years (use decimals for part years, for example 0.5 for six months).
- 4Read the interest and the total amount.
Interest = 5,000 x 4 x 3 / 100 = 600, so the total amount is 5,600. Compare the compound calculator at the same figures and you get 5,624.32: the small gap is interest-on-interest, which simple interest never charges.
- Time is entered in years; convert months to a fraction (6 months = 0.5) before entering.
- The result assumes the rate stays constant and no payments are made during the term.
- Figures are shown to two decimal places.
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus all interest already earned, so it grows faster over time.
About this tool
The Simple Interest Calculator applies the textbook formula I = P x r x t to a principal, a yearly rate and a time in years. Simple interest is still used for some short-term loans, late-payment charges and classroom problems, and this tool keeps it clean: interest on the original principal only, never on past interest.
Related tools
Part of Ovatly's free tools in Calculators.