Long-term planning

Simple Interest Calculator

Calculate simple interest earned on a principal at a fixed annual rate over a set time period. Use this Savings and investing tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
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Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Simple interest is calculated only on the principal amount using the formula I = P × r × t. Unlike compound interest, it does not earn interest on interest.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

When is simple interest used?

Simple interest is commonly used for short-term loans, car loans, and some savings accounts. Most long-term investments use compound interest.