Interest and total from principal, yearly rate and time in years, months or days. Runs on your device.
Simple interest is the principal times the yearly rate times the time in years, divided by 100: I = P × R × T ÷ 100. A principal of 10,000 at 5% a year for 3 years earns 10,000 × 5 × 3 ÷ 100 = 1,500, so the total is 11,500. The page opens on this example, and the box How this was worked out writes each step with your numbers. Interest is not compounded: each year earns the same amount, because it is always worked on the original principal. The principal can be 0 to 1,000,000,000,000 and the rate 0 to 100% a year. Numbers can be typed with commas, as in 25,000.50.
Time can be given in years, months or days. Months are divided by 12, so 18 months is 1.5 years and 5,000 at 8% earns 600. Days are divided by the number of days in a year. Banks differ here, which is why the tool asks. With 365 the calendar year is used: 2,000 at 6% for 90 days is 2,000 × 6 × (90 ÷ 365) ÷ 100 = 29.59. With 360 the banker's year of twelve 30-day months is used, which gives 30.00 for the same loan. The choice only appears when time is in days. Time may have decimals, such as 2.5 years, and must be more than 0 and no more than 100 years.
Amounts are worked in full precision and rounded to 2 decimals only when they are shown, with halves rounded up. The time in years is shown with up to 6 decimals in the working. They have no currency symbol, because the tool does not know your currency, and digit grouping follows your browser's language setting. The tool does not compound interest, add fees or tax, or count the actual days between two dates. For a loan paid back in monthly instalments, use the loan calculator instead, because a repayment schedule is a different calculation.
Lenders and savers each follow their own terms for day counts, rounding and when interest is added, so the figure here is a plain-formula estimate, not financial advice. Nothing you type is stored or sent; the numbers exist only in this tab.
I = P × R × T ÷ 100, where P is the principal, R is the yearly rate in percent and T is the time in years. For 10,000 at 5% for 3 years, I = 10,000 × 5 × 3 ÷ 100 = 1,500.00, and the total is 11,500.00.
Divide the months by 12 to get years. For 18 months, T = 1.5, so 5,000 at 8% a year earns 5,000 × 8 × 1.5 ÷ 100 = 600.00. Pick Months in Time in and type 18, and the tool does the division and shows it.
It depends on the terms of the loan or deposit. The calendar year has 365 days; some lenders use a 360-day year. For 90 days on 2,000 at 6%, 365 gives 29.59 and 360 gives 30.00. Check your own agreement, since the tool cannot know which one applies.
Simple interest is always worked on the original principal, so it grows by the same amount each year. Compound interest is worked on the principal plus interest already added. This page does simple interest only, so 10,000 at 5% earns 500 in every year.
No. The principal, rate and time stay in this tab and are not stored or sent. Reloading puts the example back. The page only records that a result was shown, without your numbers.