Simple Interest Calculator — I = P × r × t
Calculate simple interest on a loan or deposit. Enter principal, annual rate, and time (years, months, or days) — get interest earned and total balance.
Runs 100% in your browser — nothing is uploaded.
Simple interest: I = P × r × t. For interest that itself earns interest (bank accounts, most investments), use the Compound Interest calculator instead.
Frequently asked
Some short-term personal loans, most auto loans in the US (Rule of 78s notwithstanding), Treasury bills, and many bond coupons. Savings accounts and credit cards use compound interest — use that calculator instead.
Divided by 365 for the year fraction. Some contracts use a 360-day year for interest computation (called "actual/360") — this tool uses actual/365, which is more common for consumer products.
Yes — enter time as 1 month. The tool converts to years internally (1/12) and gives the interest over that period.
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