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What's a healthy BMI and waist in the UK?

Check your BMI and waist-to-height ratio against the NICE ranges the NHS uses, including the lower thresholds for some ethnic backgrounds.

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Height
Weight
How to measure your waist
  1. Find the bottom of your lowest rib and the top of your hip bone. Put the tape around your waist halfway between them.4
  2. Keep the tape level and snug, but not digging into your skin.4
  3. Breathe normally, and read it after you breathe out.4
Ethnic background (sets which NICE thresholds apply)

Adult ranges are for ages 18 and over.

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--.-BMI

Add your height and weight to see your result.

Your BMI will show on the scale above, with both sets of NICE thresholds side by side.

Why we say this

  1. BMI is weight in kg divided by height in metres, squared.10
  2. NICE NG246 (2025, updated 2026), standard thresholds: healthy 18.5 to 24.9, overweight 25 to 29.9, obesity 30 or more (class 2 from 35, class 3 from 40).1,2
  3. NICE NG246, lower thresholds for South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds: overweight 23 to 27.4, obesity 27.5 or more, with classes 2 and 3 also 2.5 lower (32.5 and 37.5).1,2
  4. NICE NG246, waist-to-height ratio (for people with a BMI under 35): 0.5 to 0.59 is increased central fat (fat around the middle), 0.6 or more is high.1

Sources checked 12 Oct 2026. Full list below.

How this works

BMI (body mass index) is your weight in kg divided by your height in metres, squared.10 You can type feet and inches, or stones and pounds; we turn them into cm and kg first (1 inch = 2.54 cm, 1 pound = 0.4536 kg, 14 pounds in a stone).

We compare your BMI with the ranges in NICE's guideline on overweight and obesity (NG246), which the NHS uses.1 NICE has two sets. The standard set calls a BMI of 25 to 29.9 overweight and 30 or more obesity. For people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background, it uses lower thresholds: 23 to 27.4 is overweight and 27.5 or more is obesity.1,2

Why two sets? People from these backgrounds tend to get weight-related illness at a lower BMI. A study of 1.5 million people in England found South Asian adults at a BMI of about 24 had the same type 2 diabetes risk as white adults at 30.5 A WHO expert group had already found in 2004 that many Asian people face higher diabetes and heart risk below a BMI of 25.6

Your waist adds what BMI misses: fat around the middle. The waist-to-height ratio divides your waist by your height, both in the same units. The NHS says to keep your waist to less than half your height.2 NICE calls 0.5 to 0.59 increased and 0.6 or more high, and suggests using the ratio for people with a BMI under 35.1 It works the same for men and women and for every background, so we don't ask your sex.

What it meansStandardNamed backgrounds
HealthyBMI 18.5 to 24.91BMI 18.5 to 22.91
OverweightBMI 25 to 29.91BMI 23 to 27.41
ObesityBMI 30 or more1BMI 27.5 or more1
Waist-to-height0.5 to 0.59 increased, 0.6 or more high (BMI under 35)1

What this can't tell you

  • How much of your weight is fat or muscle.8
  • Whether extra weight is already affecting your health. That needs a check-up, not a calculator.7
  • Anything about children or teenagers, or during pregnancy.3
  • Whether you need any treatment. On the NHS, NICE looks at BMI together with weight-related conditions, and a doctor decides.11

Questions people ask

Why does the NHS use lower BMI cut-offs for some ethnic groups?

People from some ethnic backgrounds get weight-related health problems, such as type 2 diabetes, at a lower BMI. A study of 1.5 million people in England found South Asian adults at a BMI of about 24 had the same diabetes risk as white adults at 30.5 So NICE sets lower thresholds for those groups.1

Which groups use the lower thresholds?

NICE names people with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean background. For them, overweight is a BMI of 23 to 27.4 and obesity starts at 27.5. Obesity classes 2 and 3 start 2.5 points lower too, at 32.5 and 37.5.1,2

What is a healthy waist-to-height ratio?

Under 0.5, which means a waist less than half your height.2 NICE calls 0.5 to 0.59 increased central fat (fat around the middle) and 0.6 or more high. NICE suggests using it for people with a BMI under 35.1

Is BMI accurate if I'm muscular or older?

Not always. BMI can't tell fat from muscle.3 Muscular people can read as overweight, and older adults who have lost muscle can have a BMI that hides extra fat.9,8 Your waist-to-height ratio helps in both cases.

Does a high BMI mean I need a weight-loss medicine?

No. BMI and waist describe health risk. NICE uses BMI as one part of who may be offered a medicine on the NHS, alongside weight-related conditions.11 A GP or specialist decides after looking at your whole health. Guide 3 covers all the options, from food and activity to medicines and surgery.

Can I use this for my child or teenager?

No. Adult BMI ranges are for people aged 18 and over. The NHS has a separate BMI calculator for children and teenagers aged 2 to 17, which takes age and sex into account.3

Weight and health Your options Should I consider a GLP-1? GLP-1 check: NICE and the labels Considering it for weight

Sources

  1. National Institute for Health and Care Excellence (NICE). Overweight and obesity management, NG246. Published 14 January 2025, updated 8 January 2026. Recommendations 1.9.10 (BMI classes), 1.9.11 (lower thresholds for named ethnic backgrounds) and waist-to-height ratio. nice.org.uk
  2. NHS. Obesity. Page last reviewed 29 April 2026 ("a BMI of 23 to 27.4 is overweight", "a BMI of 27.5 or higher is obese" for the named backgrounds; "keep your waist size to less than half your height"). nhs.uk
  3. NHS. BMI calculator for adults: who should not use it, muscle and fat, and the separate calculator for ages 2 to 17. Page last reviewed 28 November 2023. nhs.uk
  4. World Cancer Research Fund (UK). How to measure your waist. Checked 12 Oct 2026. wcrf.org
  5. Caleyachetty R et al. Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study. Lancet Diabetes Endocrinol 2021;9:419–26. doi:10.1016/S2213-8587(21)00088-7
  6. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet 2004;363:157–63. doi:10.1016/S0140-6736(03)15268-3
  7. Rubino F et al. Definition and diagnostic criteria of clinical obesity (Lancet Diabetes & Endocrinology Commission). Lancet Diabetes Endocrinol 2025;13:221–62. Declared interests: most of the 56 authors declare payments from Novo Nordisk, and many also from Eli Lilly (paper's own declaration). doi:10.1016/S2213-8587(24)00316-4
  8. US Centers for Disease Control and Prevention. About body mass index (BMI). Updated 16 December 2025. cdc.gov
  9. Batsis JA, Villareal DT. Sarcopenic obesity in older adults: aetiology, epidemiology and treatment strategies. Nat Rev Endocrinol 2018;14:513–37. doi:10.1038/s41574-018-0062-9
  10. Knowler WC et al.; Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med 2002;346:393–403 (defines BMI as kg divided by metres squared). doi:10.1056/NEJMoa012512
  11. NICE. Tirzepatide for managing overweight and obesity, TA1026. 23 December 2024 (an initial BMI of at least 35 with at least one weight-related condition; lower BMI thresholds, usually by 2.5, for the named backgrounds). nice.org.uk

Last checked 12 Oct 2026 · Next review due Jan 2027

How this tool was made. Built by the GLP Guidebook team from the sources above. It's general information, not medical advice. Talk to your GP or another qualified prescriber before starting, stopping or changing any treatment. How we write