Simple Interest Calculator

Work out simple interest and the final balance on any deposit or loan.

Reviewed by the WorldCalcs team · Methodology · Last reviewed: June 2026

PrincipalAnnual interest rate (%)Time (years)

Interest

1 500.00

Final balance

11 500.00

Works for any currency — results are in whatever currency you enter.

What is simple interest?

Simple interest is calculated only on the original principal, not on any interest already earned. It is common for short-term loans and some bonds.

How it's calculated

Interest = P × r × t, where P is the principal, r is the annual rate as a decimal (rate ÷ 100) and t is the time in years. Final balance = P + interest. Because the interest is not compounded, the balance grows in a straight line.

Example

10 000 at 5% for 10 years earns 5 000 in simple interest, for a final balance of 15 000.

All calculations happen in your browser. Nothing is sent, stored, or tracked.

Results are estimates and may contain errors — for general information only, not professional advice. Always verify before relying on them. Disclaimer

How to use

Enter the principal, the annual interest rate, and the time in years. The interest and final balance update instantly as you type.

Interest is the extra amount earned (or owed). Final balance is the principal plus that interest.

Frequently asked questions

What is simple interest?+

Interest charged or earned only on the starting amount, the same in every period.

How is it different from compound interest?+

Compound interest also earns interest on previously earned interest, so it grows faster over time.

When is simple interest used?+

Often for short-term or instalment loans and some bonds.

Does the interest change each year?+

No — the same amount is added every year.

Does it work for any currency?+

Yes — figures are in whatever currency you enter.