Simple Interest Calculator
Interactive StudioCalculate linear simple interest, total maturity amounts, daily/monthly accrual rates, and compare directly with compounding returns in 160+ world currencies. Instant feedback with zero server storage.
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About Simple Interest Calculator
Simple interest grows a balance in a straight line: it is calculated solely on the original principal sum using the formula I = P × r × t / 100 (where P is the principal, r is the annual rate, and t is time in years).
Unlike compound interest, previously earned interest is never added back to the principal base. This ensures a predictable, linear cost of borrowing or linear growth of fixed-term deposits.
How to use Simple Interest Calculator
- Enter the principal amount and the annual interest rate.
- Enter the time period in years.
- Read the interest earned, the total amount and the daily, monthly and yearly accrual.
Worked examples
Input: Principal 10,000, rate 5.5%, 3 years
Result: Interest 1,650.00, total 11,650.00.
Input: Principal 2,500, rate 4%, 6 months (0.5 years)
Result: Interest 50.00, total 2,550.00.
Background
Simple interest is I = P x r x t / 100. Interest is calculated only on the original principal and is never added back, so growth is a straight line over time.
Compound interest, by contrast, earns interest on interest. Over short terms the two are close, and over long terms compounding pulls far ahead. Simple interest is common in short-term loans, some bonds and car financing.
Common mistakes
- Entering months in the years field. Six months is 0.5.
- Using simple interest to estimate a savings account that compounds.
- Entering the rate as a decimal rather than a percentage.
Frequently Asked Questions
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