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BMI calculator

Work out your body mass index using metric or imperial measurements, and see which NHS/NICE weight category it falls into. Informational only: this is not a prescribing decision.

Calculate your BMI

Units
Is your family background South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean? (optional)

NICE recommends lower BMI thresholds for these groups because the risk of weight-related conditions such as type 2 diabetes rises at a lower BMI.

Calculations run in your browser. Nothing you enter is sent to us or stored.

Enter your height and weight to see your BMI. Your result will appear here.

Adult BMI categories

NHS and NICE adult BMI categories, with the lower thresholds recommended for some family backgrounds
CategoryStandard thresholdsLower thresholds*
UnderweightBelow 18.5Below 18.5
Healthy weight18.5 to 24.918.5 to 22.9
Overweight25 to 29.923 to 27.4
Obesity30 to 39.927.5 or above
Severe obesity40 or above–

*For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, as recommended by NICE.

What BMI is, and what it is not

Body mass index (BMI) compares your weight with your height. It is a quick, widely used way to screen for whether your weight may be affecting your health, and it is one of the measures the NHS and NICE use when talking about weight.

BMI has important limitations:

  • It does not distinguish muscle from fat. People with a lot of muscle can have a high BMI without carrying excess body fat, and older adults may have a “healthy” BMI while carrying more fat than it suggests.
  • It does not show where fat is stored. Fat around the waist is linked with higher health risk, which is why a healthcare professional may also measure your waist.
  • It is not for under-18s or pregnancy. Children and young people are assessed using age- and sex-specific charts, and BMI is not a reliable measure during pregnancy.
  • Risk varies with ethnicity. NICE recommends lower thresholds for some family backgrounds because weight-related conditions tend to develop at a lower BMI. Read more in our guide to BMI thresholds and ethnicity.

How BMI is used for weight-management medicines

BMI is one of several factors considered when a prescriber decides whether a weight-management medicine might be appropriate. It is never the only factor.

  • On the NHS, access to GLP-1 medicines for weight management follows NICE technology appraisals. These generally use higher BMI thresholds than the product licence, along with other criteria such as having one or more weight-related conditions. NICE reduces the BMI thresholds by 2.5 for people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background.
  • Private prescribers usually work within the product licence. At the time of writing, the licences for Mounjaro and Wegovy cover adults with a BMI of 30 or more, or 27 or more with at least one weight-related condition. Licences can change, so check the current Summary of Product Characteristics (SmPC).

In every case, a prescriber decides. They will look at your full medical history, current medicines and any reasons a medicine might not be safe for you. For more detail, see our guide to BMI and treatment eligibility.

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Frequently asked questions