Simple Interest Calculator (GCSE Maths)

This simple interest calculator is designed to help GCSE Maths students calculate interest on savings or loans using the simple interest formula. It can also be used to calculate the original principal, the interest rate, or the time period.

Simple interest is calculated only on the original amount of money, known as the principal. Unlike compound interest, the interest does not build on previous interest.

Simple Interest Formula

The simple interest formula is:

Interest = Principal × Rate × Time

Where:

• Principal (P) is the starting amount of money
• Rate (R) is the interest rate per year (as a percentage)
• Time (T) is the time in years

Worked example

Question:
£500 is invested at a simple interest rate of 4% per year for 3 years. Calculate the interest earned.

Step 1: Write down the formula
Interest = Principal × Rate × Time

Step 2: Substitute the values
Interest = 500 × 4% × 3

Step 3: Calculate
Interest = 500 × 0.04 × 3 = 60

Answer:
The interest earned is £60.

Use the calculator

Workings

Answer