Free Simple Interest Calculator

Enter principal, annual rate and years to get simple interest via the classic I = P×r×t formula — plus the total amount and yearly interest.

Principal ($)

Annual rate (%)

Time (years)

Private by design. This tool runs 100% in your browser — your inputs are never uploaded to any server.

How to Use the Simple Interest Calculator

Multiplies principal × rate × time directly (no compounding), then adds principal for the total — the transparent math behind many short-term loans.

Students learn interest basics, borrowers estimate short-term loan costs, and lenders quote simple-interest terms clearly.

Simple interest is linear — double the time, double the interest. Real bank products usually compound, so compare with the compound calculator.

What is simple interest?

Interest charged only on the original principal: I = principal × rate × time.

Simple vs compound interest?

Simple grows linearly on principal alone; compound grows faster by earning interest on interest.

When is simple interest used?

Short-term loans, some auto loans, and textbook problems — most savings compound instead.

Is the rate annual?

Yes — enter the yearly rate; time in years keeps the units consistent.