Simple Interest Calculator

Calculate simple interest with the classic P × R × T formula.

Simple Interest Calculator

Fast online calculation engine

Amount / Value 1

Rate / Percentage / Value 2

Tenure / Value 3

Output Result100010

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What does Simple Interest Calculator do?

Work out simple interest on a principal over any period, and see the total amount payable. Simple interest is charged on the original principal only, which makes it far cheaper than compound interest over long terms.

How to Use Simple Interest Calculator

1
Enter the principalThe amount borrowed or invested.
2
Enter the annual rateThe yearly interest percentage.
3
Enter the timeIn years, months or days.

Key Features

Interest and maturity amount from principal, rate and time
Time entered in years, months or days
Side-by-side comparison with compound interest on the same inputs
Solve for any variable: find the rate or time needed for a target interest

Frequently Asked Questions

What is the simple interest formula?

I = P × R × T ÷ 100, where P is principal, R is the annual rate as a percentage and T is time in years. The total amount is P + I.

How is simple interest different from compound interest?

Simple interest is always calculated on the original principal. Compound interest is calculated on the principal plus interest already earned, so it accelerates. Over 10 years at 8%, £10,000 earns £8,000 simple but £11,589 compound.

Where is simple interest actually used?

Short-term personal loans, car loans in some markets, treasury bills, and most exam questions. Long-term savings and mortgages nearly always compound.

How do I calculate interest for a number of days?

Switch the time unit to days. The calculator divides by 365, which is the common convention; some lenders use 360, so check your agreement if the amount matters.

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