Simple Interest Calculator

Work out simple interest and the final amount from principal, rate and time.

PrincipalAnnual interest rate%Timeyears

—final amount

—total interest

—principal

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About the Simple Interest Calculator

This calculates simple interest — interest charged only on the original principal, not on accumulated interest. It applies to some short-term loans, car finance, certain bonds and fixed deposits, and back-of-envelope estimates. Enter the principal, the annual rate and the time in years, and it shows the interest earned or owed and the final amount.

How it works — the formula

Simple interest uses the classic formula:

Interest = Principal × Rate × Time ÷ 100

where the rate is the annual percentage and time is in years. The final amount is principal + interest. For example, $10,000 at 5% for 3 years earns 10000 × 5 × 3 ÷ 100 = $1,500, for a total of $11,500. The interest is the same each year because it's always calculated on the original principal.

Assumptions and behaviour

Rate is per year and time is in years (use decimals for part-years — 0.5 for six months).
Interest is charged on the original principal only, never on previously-earned interest.
Currency-agnostic; amounts show two decimals.
The final amount assumes nothing is added or withdrawn during the term.

Limitations

This is simple interest, not compound. Most savings accounts, credit cards and long-term loans compound (interest on interest), which grows faster — use the Compound Interest Calculator for those.
It assumes a fixed rate and no extra deposits or repayments during the term.
It doesn't account for fees, taxes on interest, or inflation.
Make sure the rate and time use the same period (annual rate with years).

Privacy

The calculation runs entirely in your browser. Nothing is uploaded or stored.

Frequently asked questions

Is this simple interest calculator free?

Yes — free, no sign-up, no limits, runs in your browser.

What is the simple interest formula?

Interest = Principal × Rate × Time ÷ 100, where the rate is annual and time is in years. The total is principal plus interest.

How much interest on $10,000 at 5% for 3 years?

$1,500 (10,000 × 5 × 3 ÷ 100), for a final amount of $11,500. Simple interest is the same each year.

What's the difference between simple and compound interest?

Simple interest is charged only on the original principal; compound interest also charges interest on accumulated interest, so it grows faster. Use the Compound Interest Calculator for compounding.

How do I enter a period shorter than a year?

Use a decimal for the time — 0.5 years for six months, 0.25 for three months.

Does it account for tax or fees?

No. It calculates gross interest only; taxes on interest, fees and inflation aren't included.

Is my data uploaded?

No. Everything runs locally in your browser; nothing is sent or stored.

Written by Lakshay Kumar(TechLakshay)

A QA Automation Engineer by trade, Lakshay's real passion is untangling complex problems into simple, working solutions — which is exactly why FreeMyTask exists. On Instagram, he channels that same instinct into helping 26,000+ content creators with SEO education, motivation, and hands-on query solving.

Last updated: August 22, 2026