BMI healthy weight calculator

The body mass index (BMI) is a measure that uses your height and weight to work out if your weight is healthy.

Calculating your BMI

The BMI calculation divides an adult's weight in kilograms (kg) by their height in metres (m) squared.

For example, an adult who weighs 70 kg (around 11 stone) and whose height is 1.75 m will have a BMI of 22.9.

Limitations of the BMI

The BMI calculation is not suitable if you:

• have an eating disorder – please get further advice from a GP.
• are pregnant – your BMI will go up as your weight increases during pregnancy. Use your pre-pregnancy weight when calculating your BMI.
• are under 18 years old – children and young people’s weight is measured in centiles based on an average from national surveys. If you're concerned about your child's weight, see a GP.

Black, Asian and ethnic minority groups

Black, Asian and other minority ethnic groups have a higher risk of developing some long-term conditions, such as type 2 diabetes.

People from these groups with a BMI of:

• 23 or more are at increased risk
• 27.5 or more are at high risk

Muscle mass

The BMI calculation does not include muscle mass, which weighs more than fat.

This means muscular adults and athletes may be classed as overweight or obese even though their body fat is low.

Adults who lose muscle as they get older may fall into the healthy weight range even though they may be carrying excess fat.

BMI weight ranges

Underweight

Being underweight could be a sign you're not eating enough or you may be ill. If you're underweight, a GP can help.

Find out more in underweight adults

If you have an eating disorder, the BMI calculation results do not apply. Please get further advice from a GP.

Healthy weight

Find out more about having a balanced diet and find fitness videos you can try at home to maintain a healthy weight.

Overweight

If you want to lose weight, you can find more information at NHS Better Health.

Obese

Read more information about obesity. You may want to see a GP for help and advice.

Waist to height ratio

Measuring your waist to height ratio can tell you if you have excess tummy fat, even if you have a healthy BMI.

To calculate your waist to height ratio, measure your waist and divide it by your height. Use measurements in the same units (for example, centimetres or inches).

A waist to height ratio of 0.5 or higher means you may have increased health risks such as heart disease, type 2 diabetes and stroke.

To measure your waist:

1. Find the bottom of your ribs and the top of your hips (just above your belly button).
2. Wrap a tape measure around your waist midway between these points.
3. Breathe out naturally before taking the measurement.