Simple Interest Calculator
Planning simple Interest is easier when the main numbers are in one place. Add your figures to the Simple Interest Calculator, then read the notes below the result to see what is included.
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Last reviewed January 15, 2026 — see our editorial & accuracy policy.
Method: Interest = principal × rate × time; the balance grows linearly because interest is never added to the base.
How it works
Simple interest is calculated only on the original principal:
Interest = Principal × Rate × Time ÷ 100
The final amount is the principal plus the interest. Unlike compound interest, simple interest does not earn interest on previously added interest.
How to use the Simple Interest Calculator
Enter the values requested by the tool and start with one realistic example. Read the result together with its unit or label, then change one input at a time if you want to compare options. Keeping a note of the original figures makes the calculation easier to check later.
Use the result as a planning estimate rather than a quote or guarantee. Rates, fees, tax rules and personal circumstances can change the final figure.