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Computes flat interest from principal, rate and time without compounding. Use for short-term loans or quick estimates; differs from compound-interest-calculator by linear growth vs compounding. Returns interest, total payable and split. 100% client-side.
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Calculates simple interest on a principal amount over a period of years. Unlike compound interest, interest is only ever calculated on the original principal, so you can see the total interest and final amount clearly.
Simple interest is used for many personal loans, promissory notes, and short-term lending. Seeing the total interest and final amount makes the true cost of borrowing — or the return on lending — transparent.
This tool is part of the DevStackIO platform — a collection of free online developer tools from DevStackIO. Browse more free developer resources on DevStackIO.
Borrowers of simple-interest personal loans, savers with simple-interest deposits, and finance students checking their math.
Enter the principal amount
Enter the annual interest rate as a percent
Enter the time period in years
Read the interest and the total
Convert months to years (divide by 12) for partial terms
Compare against a compound-interest tool to see the difference
$10,000 at 5% for 3 years → interest $1,500, total $11,500$1,000 at 8% for 2 years → interest $160, total $1,160$50,000 at 4% for 5 years → interest $10,000, total $60,000$2,500 at 6% for 9 months → interest $112.50, total $2,612.50Does this tool support multiple currencies?
Yes, select your currency from the dropdown. All calculations run locally in your browser.
What's different from compound interest?
Interest is only charged on the original principal, never on accumulated interest.
What uses simple interest?
Many personal loans, auto notes, and short-term instruments.
How do I convert months?
Enter months/12 as the time in years.
Is my data shared?
No, everything runs locally in your browser.
Why is simple interest lower than compound?
Because it never earns interest on interest, so the total grows only from the original principal.
Can a loan be simple interest but still have fees?
Yes, fees are usually separate from the interest calculation.
Authoritative specifications, standards, and in-depth reading for Simple Interest Calculator.
Interest earned
$1,500.00
Total owed/kept
$11,500.00
Principal
$10,000.00
Not financial advice
The results from this calculator are provided for general informational and educational purposes only. They are estimates based on the assumptions you enter and do not constitute financial, tax, legal, or investment advice, nor a recommendation to buy, sell, or hold any financial product. Tax codes, rates, and regulations change frequently and vary by country, state, and local jurisdiction — and may differ based on your individual circumstances, employer plan rules, and provider policies. Always verify the figures with current official sources and consult a qualified financial, tax, or legal professional before making any financial decision. All calculations run privately in your browser; nothing you enter is sent to our servers.
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