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Simple interest calculator

Enter a sum, an annual rate and a period in years. The calculator works out the simple interest and the total amount.

Result

Interest earned

Total amount

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This calculation is for informational purposes only and does not replace advice from a qualified professional. Formulas and rates may not fit your exact situation — double-check the figures before making decisions.

How it is calculated

Simple interest = sum × rate ÷ 100 × years. Interest accrues every year only on the original sum — unlike compound interest, past years' interest doesn't itself earn new interest here.

Because of that, growth under simple interest is linear, not accelerating: 10% a year in simple interest over 10 years gives exactly 100% total growth, not more — compare that to compound interest, where the same rate over 10 years would give noticeably more than 100% specifically because interest earns interest.

In practice, most deposits, investments and loans use compound interest, not simple — simple interest shows up more often in specific contract terms, short-term loans, or legally defined penalty interest where it's explicitly stated to be simple. Before using this calculation for a real financial product, it's worth checking which type of interest it actually specifies — otherwise the result can diverge noticeably from reality.

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