Finance
Simple Interest Calculator
Interest and total payable on a fixed-rate loan.
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CalcoTools · Simple Interest Calculator · generated 8/23/2026, 1:08:38 PM
About the Simple Interest Calculator
Calculates interest that accrues only on the original principal — unlike compound interest, it never earns interest on previously earned interest, which makes it simpler (and slower-growing) to work out by hand.
How to use it
- Enter the Principal amount.
- Enter the annual Rate (% p.a.).
- Enter the Time in years.
- Read the interest and total payable in the result panel.
Formula
Interest = (Principal × Rate × Time) ÷ 100
Total payable = Principal + Interest
The standard simple-interest formula (I = PRT), the textbook counterpart to the compound-interest formula used in the Compound Interest Calculator.
Worked example
A $10,000 loan at 6% simple interest for 3 years accrues $1,800 in interest, for a total payable of $11,800.
Recommendations
- • Confirm whether your loan or investment actually uses simple interest — most modern products use compound interest instead.
- • Simple interest is easy to sanity-check by hand: rate × time × principal, no exponents involved.
- • For a more realistic projection on savings or loans that compound, use the Compound Interest Calculator instead.
Frequently asked questions
Mostly for short-term loans, certain bonds, and some auto loans. Most mortgages, credit cards, and savings accounts use compound interest instead, which grows faster over time.
Disclaimer
Illustrative estimate only, not financial or tax advice. Verify figures with a licensed adviser or your local tax authority.