$10,000
6%
5 Years
Home › Calculator Tools › Simple Interest Calculator
Calculate simple interest on any principal — and solve for any missing variable: find rate, time, or principal from the other three.
Simple Interest Calculator · compounding interest comparisons · 100% private
Principal, annual interest rate, time period, and total interest. Leave the one you want to find blank.
The missing value is solved for instantly.
Principal, total interest, and final amount (principal + interest) are all displayed.
Simple Interest = P × R × T / 100, where P is the principal amount, R is the annual interest rate (as a percentage), and T is the time in years. The total amount repaid is P + SI. Unlike compound interest, simple interest does not earn interest on previously accrued interest.
Simple interest is used in short-term loans, certain government bonds, some fixed deposits with short tenures, consumer credit, and car loans in some markets. Many educational and regulatory contexts also use it as the basis for consumer credit comparisons (APR calculations for short-term credit).
Rate = (SI × 100) / (P × T). Leave the Rate field blank and enter Principal, Time, and the known Total Interest — the calculator solves for Rate automatically.
No. All calculations run in your browser. No data is transmitted.
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Simple interest is the foundational concept behind all interest calculations — and it’s still directly applicable in many real-world contexts, from short-term personal loans to some fixed-income instruments. This calculator lets you solve for any of the four variables in the simple interest formula: given any three, it finds the fourth. That makes it useful both for standard calculations (what interest accrues on £5,000 at 7% over 3 years?) and for reverse calculations (at what rate did I need to invest to earn £500 interest on £4,000 over 2 years?). The missing-variable approach makes it more flexible than a one-directional calculator.
All calculations run in your browser. No data is transmitted to any server.