Estimate simple interest from a starting amount, annual interest rate, and time in years. See the interest amount and ending balance without compounding.
$1,000 x 5% x 3 years
This is not APR, compound interest, amortization, a lender payoff quote, or a bank statement. Use it only when the simple principal x rate x time setup matches the question.
Calculate simple interest for classwork, worksheets, or quick planning.
Estimate interest when interest does not earn more interest.
Compare a straight simple-interest result with compound interest.
Check a principal-rate-time example before reading a loan, savings, or disclosure document.
$150 interest, $1,150 ending balance
$234.38 interest, $2,734.38 ending balance
$240 interest, $12,240 ending balance
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Plain-language answers about when to use the estimate, what your numbers mean, what is left out, and how privacy works.
Use it when you want to test the exact inputs on this page: Calculate simple interest for classwork, worksheets, or quick planning. Estimate interest when interest does not earn more interest. The result is a check against your assumptions, not proof that a lender, tax app, broker, platform, or provider will use the same number.
Principal means the starting amount before interest is added. Annual interest rate means the yearly rate as a percent. Enter 5 for 5%, not 0.05. Time in years means how long the money earns or owes simple interest. Use 1.5 for 18 months or 0.25 for 3 months.
Simple interest is principal x annual rate x time. A $1,000 principal at 5% for 3 years gives $1,000 x 0.05 x 3, or $150 interest.
No. APR can include fees and timing rules. This calculator only multiplies principal, annual interest rate, and years.
Use compound interest when interest gets added to the balance and then earns more interest. Simple interest keeps the interest separate from the principal.
In plain language: Simple interest equals principal x annual rate x time. The ending balance equals principal plus simple interest. For the starter example, $1,000 x 0.05 x 3 equals $150 simple interest. The ending balance is $1,000 + $150 = $1,150.
Read the interest amount first, then the ending balance. The ending balance is not a payment schedule, payoff quote, APR, or compound-growth result.
This is straight principal-rate-time math. It is not APR disclosure, amortization, compound interest, daily balance interest, lender payoff math, bank disclosure, tax advice, or a quote. Use the lender, bank, or school worksheet when a real decision depends on APR, compounding, fees, taxes, due dates, payments, or daily balance rules.
Check that the rate is annual, the time is in years, and the percent is entered as 5 for 5%. Use 1.5 for 18 months and 0.25 for 3 months.
No. The calculator runs in your browser tab. Recent answers stay only on the page while you use it, and they are not sent to a server.