Measuring your weight

Body Mass Index (BMI)

One of the most common ways to find out if you’re at a healthy weight is by working out your Body Mass Index (BMI).

BMI is a measure that adults can use to see if they’re a healthy weight for their height.

Calculate your BMI using the NHS BMI calculator. Before you start you'll need an accurate measurement of your height and weight.

You can also use the calculator to check your child’s BMI. For children and young people aged 2 to 18 it also takes into account age and gender as well as height and weight.

Once you know your BMI you can check on the NHS website to find out what it means for you and/or your child.

Limitations of BMI

BMI is a good indicator to show if you’re carrying too much or too little weight, but it cannot tell if you’re carrying too much fat.

The adult BMI does not take into account age, gender or muscle mass. So, when calculating your BMI you should take into consideration that:

  • athletes and very muscular adults who play a lot of sport can have a BMI of over 25 even though their body fat is low
  • adults who lose muscle as they get older may still carry excess fat even though their BMI says that they’re a ‘healthy’ weight

You should use your BMI result as a starting point for:

  • making healthy changes to your diet and lifestyle if you’re over or under the recommended BMI for your age and height
  • speaking with your GP if you’re concerned about your weight and need some advice