Calculate your body mass index (BMI) for adults

Use this service to:

  • check the BMI of an adult aged 18 and over
  • get information about what to do next

You should not use this tool to diagnose any symptoms. If you are worried about your weight, contact your local pharmacist or GP surgery.

Who should not use this tool

You should not use this tool if you, or the person you're using it for:

  • are under 18 years old
  • are pregnant
  • have been diagnosed with an eating disorder, or think you may have one
  • have a condition that affects your height
Information:

If you or your child are aged between 2 and 17, calculate BMI for children and teenagers.

What you will need

To use the calculator, you will need to know your:

  • height
  • weight

Ethnic background

The calculator will also ask for information on your ethnic background.

This is because people from an Asian, Black African, African-Caribbean or Middle Eastern ethnic background have a higher chance of developing health problems at a lower BMI.

When you enter information on your ethnic background, the calculator will give you more accurate advice about your BMI result.

Your result

Your BMI result will be displayed as a number with one of these weight categories:

  • underweight
  • a healthy weight
  • overweight
  • obese

After getting your result, you may be asked to measure your waist. This can help you understand if you are carrying too much weight around your tummy.

How your BMI is calculated

The BMI is calculated by dividing an adult's weight in kilograms by their height in metres squared.

For example, if you weigh 70kg (around 11 stone) and are 1.70m (around 5 foot 7 inches) tall, you work out your BMI by:

  1. squaring your height in metres: 1.70 x 1.70 = 2.89
  2. dividing your weight in kilograms: 70 ÷ 2.89 = 24.22

Your result will be displayed to one decimal place, for example, 24.2.

What your result means

A higher BMI increases the chance of developing long-term conditions, such as type 2 diabetes and heart disease.

The BMI calculation is just one measure of health. It cannot tell the difference between muscle and fat.

For example, if you have a lot of muscle, you may be classed as overweight or obese despite having low body fat.

This is why you may get a better idea of your overall health from measuring your waist.

Start now

By using this tool you agree to our terms and conditions.

Page last reviewed: 28 November 2023
Next review due: 28 November 2026