The three obesity classes are: class 1 BMI 30–34.9, class 2 BMI 35–39.9 and class 3 BMI 40 or more (NICE NG246). For South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean adults, obesity starts at 27.5, class 2 at 32.5 and class 3 at 37.5. A BMI of 37, for example, is class 2 obesity for most adults.
Check your BMI and obesity class
Obesity classes explained
| Class | BMI (most adults) | BMI (lower thresholds*) | Other names |
|---|---|---|---|
| Class 1 | 30 – 34.9 | 27.5 – 32.4 | Moderate obesity |
| Class 2 | 35 – 39.9 | 32.5 – 37.4 | Severe obesity |
| Class 3 | 40 or more | 37.5 or more | Very severe obesity (formerly “morbid obesity”) |
*South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background (NICE NG246).
In England, 29% of adults were living with obesity in 2022 (Health Survey for England). Obesity is recognised by the NHS and NICE as a long-term condition with many causes – genes, environment, sleep, stress, medicines and life events – not simply a matter of willpower.
What weight is each obesity class?
These are the weights where each class begins for common heights.
| Height | Class 1 (BMI 30) | Class 2 (BMI 35) | Class 3 (BMI 40) |
|---|---|---|---|
| 5′0″ (152 cm) | 69.7 kg · 11 st 0 lb | 81.3 kg · 12 st 11 lb | 92.9 kg · 14 st 9 lb |
| 5′2″ (157 cm) | 74.4 kg · 11 st 10 lb | 86.8 kg · 13 st 9 lb | 99.2 kg · 15 st 9 lb |
| 5′4″ (163 cm) | 79.3 kg · 12 st 7 lb | 92.5 kg · 14 st 8 lb | 105.7 kg · 16 st 9 lb |
| 5′6″ (168 cm) | 84.3 kg · 13 st 4 lb | 98.4 kg · 15 st 7 lb | 112.4 kg · 17 st 10 lb |
| 5′8″ (173 cm) | 89.5 kg · 14 st 1 lb | 104.4 kg · 16 st 6 lb | 119.3 kg · 18 st 11 lb |
| 5′10″ (178 cm) | 94.8 kg · 14 st 13 lb | 110.6 kg · 17 st 6 lb | 126.5 kg · 19 st 13 lb |
| 6′0″ (183 cm) | 100.3 kg · 15 st 11 lb | 117.1 kg · 18 st 6 lb | 133.8 kg · 21 st 1 lb |
| 6′2″ (188 cm) | 106.0 kg · 16 st 10 lb | 123.7 kg · 19 st 7 lb | 141.3 kg · 22 st 4 lb |
Health risks by obesity class
The NHS lists many conditions linked with obesity, including type 2 diabetes, coronary heart disease, some cancers (such as breast and bowel cancer), stroke, fatty liver disease, osteoarthritis, sleep apnoea, reduced fertility and low mood. The risk rises with each class, and is higher again when weight is carried around the waist.
Class 1
Clearly raised risk of type 2 diabetes and high blood pressure. Losing 5–10% of body weight can make a big difference.
Class 2
Higher risk of heart disease, sleep apnoea and joint problems. Specialist help is more likely to be offered.
Class 3
The highest risk of complications and reduced life expectancy. Specialist services, medicines or surgery may be options.
NHS support for each class
Support depends on your BMI, any related health conditions and what is available locally. Your GP or pharmacist is the best place to start.
- All classes: the free NHS Weight Loss Plan app, local council or GP-referred weight management programmes (often 12 weeks), and the NHS Digital Weight Management Programme if you have diabetes or high blood pressure.
- Specialist weight management services: for people with more complex needs, usually with a BMI of 35 or more (or lower for some ethnic groups) and related conditions.
- Weight loss medicines: NICE recommends medicines such as semaglutide (Wegovy) and tirzepatide (Mounjaro) only for people who meet specific criteria, which include BMI thresholds and having at least one weight-related condition, alongside diet and activity support.
- Weight loss surgery: usually considered for people with a BMI of 40 or more, or 35 to 40 with a significant condition such as type 2 diabetes, who have tried other approaches (NICE NG246). People with recently diagnosed type 2 diabetes may be assessed at a lower BMI.
Buying weight loss medicines online? Only use a UK-registered pharmacy and a prescriber who checks your medical history. Never buy injections from social media or unregulated websites.
Moving down an obesity class
Moving from class 2 to class 1, or out of the obesity range altogether, brings real health benefits – but even smaller changes count. NICE highlights that losing 5% to 10% of body weight improves blood pressure, cholesterol and blood sugar.
Use the weight loss timeline calculator to see how long each step might take at a safe rate of 0.5–1 kg a week, and the weight loss percentage calculator to track progress.
Frequently asked questions
What are the 3 classes of obesity?
Class 1 is a BMI of 30 to 34.9, class 2 is 35 to 39.9 and class 3 is 40 or more. For some ethnic groups, the thresholds are 27.5, 32.5 and 37.5.
What obesity class is a BMI of 37?
A BMI of 37 is class 2 obesity for most adults. For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, it is also class 2 (32.5–37.4). See BMI of 37.
Is class 1 obesity serious?
Class 1 obesity increases the risk of conditions such as type 2 diabetes, high blood pressure and heart disease. It is very treatable, and losing even 5% of your weight lowers these risks.
What BMI is classed as severely obese?
A BMI of 40 or more is class 3 obesity, sometimes called severe or very severe obesity. NICE uses 37.5 for some ethnic groups.
Can I get weight loss injections on the NHS?
Some people can, if they meet NICE criteria, which include BMI thresholds and having at least one weight-related condition. They are given with diet and activity support, often through specialist services. Ask your GP.
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Medical disclaimer: this guide is general information for adults and is not a diagnosis or medical advice. bmicalculatornhs.net is independent and not affiliated with the NHS. Speak to your GP, pharmacist or another qualified health professional about your own health. Full disclaimer.