Simple Interest Calculator
Works out simple interest from the principal, annual rate and time.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
interest = principal × rate × time
Simple interest is only ever calculated on the original amount, so it grows in a straight line.
What to watch out for
Simple interest is used on some short-term and flat-rate loans, and on bonds that pay out their interest. Most monthly-repayment loans charge interest on the falling balance instead, so use the loan calculator for those. For time in months, enter it as a fraction of a year: 18 months is 1.5.
Frequently Asked Questions
How do I calculate simple interest?
Multiply the principal by the rate and the time. 10,000 at 5% for 3 years earns 1,500.
What is the difference between simple and compound interest?
Compound interest also earns interest on past interest. Over 3 years at 5%, 10,000 earns 1,500 simple but 1,576.25 compounded yearly.