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ToolWrenCalculate simple interest and the final repayable amount from a principal, annual rate and time in years.
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Simple Interest is a free, private online tool that lets you calculate simple interest and the final amount from principal, rate and time. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
Simple interest is charged only on the original principal, not on accumulated interest. It is common for short-term loans and some bonds.
Interest = principal x rate x time / 100. The final amount is principal plus interest.
Quick loan estimates, savings comparisons and understanding short-term interest.
Simple interest is interest calculated only on the original amount you borrow or invest — the principal — and never on interest already accrued. It is the most basic way interest is charged, common on short-term loans, some car finance and certain bonds, where the interest does not snowball the way compound interest does.
Simple interest uses one clean formula: Interest = Principal x Rate x Time, where the rate is the annual percentage and time is in years. So 1,000 at 5% for 3 years earns 1000 x 0.05 x 3 = 150 in interest, for a final total of 1,150. The tool computes both the interest and the final amount instantly.
The crucial difference is what the interest is calculated on. Simple interest always uses the original principal, so it grows in a straight line. Compound interest is calculated on the principal plus previously earned interest, so it accelerates. Over short periods the two are close, but over many years compound interest pulls far ahead.
You will meet simple interest on short-term and fixed-term products: many personal and car loans, bridging finance, treasury bills, and some promotional offers. It is also how late-payment interest is often calculated. Knowing the formula lets you check a lender's figures and compare offers fairly.
Estimate the cost of a short-term loan, the return on a fixed-rate bond, or the interest on a deposit. Because it is a straight calculation, it is also a good way to understand how interest works before tackling compounding. Everything is calculated in your browser.