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Waist-to-height ratio: what it measures and what the numbers mean

Keep your waist to less than half your height. That one sentence is the whole idea behind waist-to-height ratio, and since 2025 NICE has recommended it alongside BMI for most adults in England, to show where they carry weight.

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What it is

Waist-to-height ratio (often shortened to WHtR) is your waist circumference divided by your height, both in the same units:

waist-to-height ratio = waist ÷ height

Someone 175 cm tall with an 84 cm waist has a ratio of 84 ÷ 175 = 0.48. With a 92 cm waist the same person is at 0.53. Because it is a ratio, it works the same in inches as in centimetres. The only rule is not to mix them.

It exists because BMI cannot see where weight sits. Two people with the same height and weight have the same BMI whether their weight is carried as muscle, around the hips, or around the middle. Fat carried centrally, around the abdomen, is the kind most closely linked with heart disease and type 2 diabetes, and a tape round the waist is the simplest way to see it.

How to measure your waist

The NICE guideline gives this method:

  1. Find the bottom of your ribs and the top of your hips.
  2. Wrap a tape measure around your waist midway between those two points. For most people that is just above the belly button.
  3. Breathe out naturally, then take the measurement.

That midway point is not always where your trousers sit, and it is not always the narrowest part of your waist. What matters most is using the same spot every time, with the tape level and snug but not pressing in. Measure at a similar time of day, because a meal or a drink changes the reading.

What the numbers mean

NICE, which writes the guidance the NHS in England follows, sorts adults into three groups:

  • 0.4 to 0.49 Healthy central adiposity — no increased health risks
  • 0.5 to 0.59 Increased central adiposity — increased health risks
  • 0.6 or more High central adiposity — further increased health risks

The same boundaries apply to men and women and to all ethnic groups. That makes WHtR simpler than waist size on its own, whose cut-offs differ by sex and ethnicity. NICE does not give a label for readings below 0.4, so this page does not either.

The public version of the message is the one at the top of this page: keep your waist to less than half your height. It comes from a 2005 paper by Margaret Ashwell and Shiun Dong Hsieh arguing that one simple boundary could work worldwide. A 2012 systematic review and meta-analysis by Ashwell and colleagues concluded that WHtR is a better screening tool for adult cardiometabolic risk factors than waist circumference or BMI.

Who it is for, and who it is not

NICE recommends measuring and using waist-to-height ratio as well as BMI in adults whose BMI is below 35. It is not meant to replace BMI. The NHS's own waist-to-height calculator says it is not suitable for:

  • children under 5
  • anyone who is pregnant
  • people with an eating disorder or a growth disorder
  • adults with a BMI over 35

For children and young people aged 5 and over, NICE uses the same three bands.

One common claim needs correcting. NICE does warn that BMI should be read with caution in people with a lot of muscle, and in adults aged 65 and over. That warning is about BMI, not about waist-to-height ratio, which is part of the reason for measuring the waist at all.

It is not only the NHS

WHtR has spread well beyond medicine. From January 2026 the US military adopted it as its body-composition screen: a service member whose ratio is below 0.55 passes, and anyone at or above it gets a fuller body-fat assessment. The US Army has since made WHtR its only screening measurement, replacing the tape-measure body-fat formulas it used before. The 0.55 figure is a fitness-for-service standard, not a health band, so do not read it against the NICE groups above.

What it cannot tell you

  • It is a screening measure, not a diagnosis. A reading in the increased or high group is a reason to talk to a GP or practice nurse. It says nothing definite about your health.
  • It does not measure fat directly. A waist measurement includes everything under the tape: muscle, organs, and whatever you ate for lunch.
  • A single reading is noisy. Where the tape sits, how you breathe and when you last ate can each move it. A ratio tracked over months, measured the same way each time, tells you far more than one number does.

Sources

  • NICE. Overweight and obesity management, guideline NG246, published 14 January 2025 (recommendations 1.9.3, 1.9.8, 1.9.12–1.9.15, 1.10.5, 1.10.10 and Box 1). nice.org.uk/guidance/ng246
  • NHS. “Calculate your waist to height ratio”, reviewed 25 February 2025. nhs.uk
  • Ashwell M, Hsieh SD. “Six reasons why the waist-to-height ratio is a rapid and effective global indicator for health risks of obesity…” International Journal of Food Sciences and Nutrition, 2005;56(5):303–307.
  • Ashwell M, Gunn P, Gibson S. “Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis.” Obesity Reviews, 2012;13(3):275–286.
  • US Under Secretary of Defense for Personnel and Readiness. “Additional guidance on military fitness standards”, memorandum of 18 December 2025 (WHtR below 0.55, from 1 January 2026); and US Army Directive 2026-13, Army Body Composition Program.

This page is reference information about how a measurement is taken and what the research says about it. It is not medical advice, and no figure on it is a diagnosis. Talk to a doctor, nurse or registered dietitian about your own health.