Free patient tool
Am I eligible for weight-loss surgery?
Enter your height and weight to see your BMI, whether you may be eligible for surgery under UK and international guidelines, and how much weight people typically lose with each option.
- Instant, live results
- Kilograms or stones
- Based on NICE and international guidelines
Your details
Height
Weight
Your BMI
38.1
Obesity (class 2)
You may be a candidate for weight-loss surgery
International guidelines (ASMBS and IFSO) recommend surgery from a BMI of 35. In the UK, surgery at this BMI is usually offered when you also have a weight-related health condition.
| Treatment | Estimated weight | Weight loss |
|---|---|---|
| Gastric bypass (after 1 year) | 76 kg | 34 kg |
| Gastric sleeve (after 1 year) | 83 kg | 28 kg |
| Gastric balloon (after 6 months) | 99 kg | 11 kg |
Surgery figures are average total body weight loss from a large US study (PCORnet, 2018); gastric balloon figures are from FDA approval data. Your results depend on your health and lifestyle.
Free assessment
Talk to a bariatric specialist
Send us your result and a specialist will review your options with you, free and without obligation.
Ask on WhatsAppThis calculator is for general guidance only and is not a medical diagnosis. Eligibility is based on UK NICE guidance and international ASMBS/IFSO recommendations; a specialist will confirm what is right for you.
How this calculator works
- Your BMI is calculated from your height and weight. You can switch between kilograms and centimetres, or stones and feet.
- Eligibility follows UK NICE guidance: usually a BMI of 40 or more, or 35 to 39.9 with a weight-related condition, and from 30 with recent type 2 diabetes.
- International ASMBS and IFSO guidelines recommend surgery from a BMI of 35, which we also show.
- For people of South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, UK guidance lowers these thresholds by 2.5.
- Weight-loss estimates use average results: about 31% of body weight after 1 year for gastric bypass and 25% for gastric sleeve (PCORnet study, 2018), and about 10% after 6 months for a gastric balloon (FDA data).
Frequently asked questions
In the UK, surgery is usually considered with a BMI of 40 or more, or between 35 and 39.9 with a weight-related condition such as type 2 diabetes or high blood pressure. Lower thresholds apply for some family backgrounds.
A gastric balloon is usually offered from a BMI of about 27 to 35, and occasionally up to 40. A specialist will check whether it suits you.
On average, people lose about 31% of their body weight in the first year after a gastric bypass and about 25% after a gastric sleeve. Your result depends on your health and the changes you make.
No. It is a guide based on published guidelines and averages. A specialist will review your full medical history before recommending any treatment.
