Math calculator
Simple Interest Calculator
Calculate simple interest and the total balance from principal, rate, and time.
How this calculation works
Interest = principal × annual rate × time (rate as a decimal; time in years). Use the calculator above to enter your values. Inputs are checked before a result is shown, and calculations run locally in your browser.
$1,000 at 5% for 3 years: $150 interest; $1,150 total.
$5,000 at 4% for 2 years: $400 interest; $5,400 total.
$1,200 at 3.5% for 4 years: $168 interest; $1,368 total.
Frequently asked questions
How does the simple interest calculator work?
Interest = principal × annual rate × time (rate as a decimal; time in years).
What is an example?
$1,000 at 5% simple interest for 3 years earns $150 interest and totals $1,150.
Can I enter decimal values?
Yes. Enter decimal values where appropriate. The calculator checks required inputs and displays a readable result.
Are results rounded?
Results are formatted for readability. Check the displayed formula and units when using the result.
Keep calculating