BMI Calculator
Body Mass Index compares your weight with your height.
It takes about ten seconds to work out, and it gives you and your clinician a shared starting point for a conversation about your health.
Work out your BMI
Body Mass Index compares your weight with your height.
It takes about ten seconds to work out, and it gives you and your clinician a shared starting point for a conversation about your health.
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BMI calculator
Body Mass Index is a general measure that compares your weight with your height. Enter your details below to see your figure.
BMI is a general guide only and does not account for muscle mass, build or body composition. It is not a diagnosis. If you have any concerns about your weight or your health, speak to your GP. Your suitability for any procedure is assessed by a clinician at consultation.
Common questions
BMI, answered
The figure is a starting point. These are the questions people most often ask once they have it.
No. The same ranges are used for adult men and women. Body composition does differ between men and women, which is one of the reasons BMI is treated as a starting point rather than a complete picture of your health.
Yes. NICE advises that people of Asian, Black African, African Caribbean and Middle Eastern family background may be at increased health risk at a lower BMI than the standard ranges suggest.
For these groups, 23 is often used as the point where risk begins to increase, and 27.5 as the point where it increases further. If this applies to you, discuss your figure with your GP or clinician.
BMI does not distinguish between muscle and fat. Muscle is denser than fat, so people who are very muscular can record a high BMI while carrying very little excess weight.
This is a recognised limitation of the measure, and it is why clinicians look at BMI alongside other factors rather than on its own.
No. BMI is assessed differently for anyone under 18, because children and young people are measured against growth charts that account for age and sex. This calculator is for adults only.
Speak to your GP or practice nurse if you have any concerns about a child's weight.
No. BMI is not a reliable measure during pregnancy. Your midwife or GP will monitor your weight as part of your antenatal care.
It becomes less reliable with age, as both muscle mass and height can change over time. Adults over 65 should treat the figure with caution and discuss it with their GP.
Waist to height ratio is now recommended by NICE as a useful additional measure. You divide your waist measurement by your height, using the same units for both, and a figure below 0.5 is generally used as the guide.
A clinician will also consider your medical history, blood pressure, blood tests and lifestyle.
In the UK, weight loss surgery is generally considered for adults with a BMI of 40 or above, or a BMI of 35 or above alongside a related health condition such as type 2 diabetes or high blood pressure. Lower thresholds may apply in some circumstances, including for people from certain ethnic backgrounds.
BMI is only one part of the assessment. Your suitability for any procedure is determined by a clinician at consultation.
No. The calculation runs entirely in your browser. Nothing you enter is saved or sent to us.
Book an appointment with your GP. They can put the figure in the context of your wider health, arrange any tests they feel are appropriate, and talk you through the options available to you.
This page is for information only. It is not a diagnosis and it does not replace advice from a qualified clinician. If you have any concerns about your weight or your health, speak to your GP.