How to use the Waist-to-Height Ratio
- Measure your waist at the level of the navel, standing relaxed, at the end of a normal breath out — not sucked in.
- Use a non-stretch tape held level all the way round, snug against the skin without compressing it.
- Enter waist and height in the same system; the calculator handles centimetres and shows the inch equivalents.
- Read the ratio against the risk bands and note the target waist size shown for your height.
- Re-measure monthly at the same time of day rather than daily — waist moves slowly and daily noise is mostly bloating.
How the calculation works
The ratio is waist divided by height, and the boundary that matters is 0.5. The rule of thumb, 'keep your waist to less than half your height', works because it is dimensionless: it scales automatically across adults of different sizes and across most ethnic groups, which is exactly where fixed waist thresholds such as 94 cm or 102 cm break down.
Waist-to-height beats BMI on the thing BMI is worst at — distinguishing where mass sits. Two people at BMI 27 can have very different visceral fat volumes, and it is visceral fat, not subcutaneous fat, that is metabolically active and associated with insulin resistance, dyslipidaemia and hypertension. Ashwell's meta-analyses found waist-to-height a better discriminator of cardiometabolic risk than both BMI and waist circumference alone.
Bands used here follow the commonly published boundaries: below 0.4 suggests being underweight for your frame, 0.4 to 0.5 is the healthy zone, 0.5 to 0.6 signals increased risk and above 0.6 high risk. Children and adolescents use the same 0.5 boundary from about age six, which is one reason clinicians like it. It remains a screen, not a diagnosis — measurement technique varies enough that a change of a centimetre or two should not be over-read.
WHtR = waist ÷ height; healthy target waist = 0.5 × heightSource: Ashwell M, Gunn P, Gibson S, 'Waist-to-height ratio is a better screening tool than waist circumference and BMI', Obesity Reviews (2012); NICE guideline CG189 update (2022) adopting the 0.5 boundary.
Worked example
Someone 178 cm tall with an 86 cm waist.
- Ratio = 86 ÷ 178 = 0.483.
- That sits in the 0.4–0.5 healthy band.
- Target waist = 0.5 × 178 = 89 cm, so there is 3 cm of headroom.
A ratio of 0.483 — healthy, with the boundary reached at an 89 cm waist.
Frequently asked questions
Where exactly should I measure my waist?+
At the level of the navel, or midway between the lowest rib and the top of the hip bone. Pick one and stay with it — consistency matters more than which landmark you use.
Is this better than BMI?+
For cardiometabolic screening, generally yes. BMI cannot tell muscle from fat or belly fat from hip fat; waist-to-height captures central adiposity, which carries most of the risk.
Does it apply to children?+
The 0.5 boundary is used from roughly age six upward, which is unusual — most adult thresholds do not transfer to children at all.
My ratio is under 0.4. Is that a problem?+
It can indicate being underweight for your frame. Combine it with BMI and a clinician's view rather than treating a low number as automatically better.
Last reviewed September 1, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.