Simple Interest Calculator

Simple interest is charged only on the original principal. Use this calculator to find the interest and total amount, or work backwards to the principal, rate or time needed for a given amount of interest.

How to use the Simple Interest Calculator

1. Choose what to solve for: interest, principal, rate or time.
2. Fill in the other three values.
3. Pick years, months or days for the time period.
4. Press Calculate to see the answer and the total.

Features

• Solve for any of the four variables
• Time in years, months or days (365-day year)
• Shows principal, rate, time, interest and total together

Benefits

• Check short-term loans, deposits and bonds that use simple interest
• Learn the relationship between principal, rate and time

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is calculated only on the original principal. Compound interest is also earned on previously added interest, so it grows faster over time.

How are days converted?

Days are divided by 365. Some lenders use 360 days, which gives slightly more interest. Results are estimates for planning and education, not financial advice.

Can I find how long it takes to earn a certain interest?

Yes. Choose "Time", enter the principal, rate and interest target, and the calculator returns t = I ÷ (P × r).

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