Waist-to-Height Ratio (WHtR) Calculator

Waist-to-height ratio (WHtR) is one of the easiest health screens you can do at home. You divide your waist circumference by your height, both measured in the same unit:

WHtR = waist ÷ height

Because it divides one length by another, the unit cancels out — centimetres or inches give the same number. The headline public-health message comes from the UK's NICE Guideline NG246: keep your waist to less than half your height. In ratio terms that is a target of WHtR below 0.50. NICE recommends using it alongside BMI for adults with a BMI under 35.

The calculator refines that single rule into four bands published by Ashwell and Gibson in BMJ Open (2016), drawn from a large review of WHtR and health outcomes:

• Below 0.40 — take care (possibly too low)
• 0.40 to 0.49 — healthy
• 0.50 to 0.59 — increased risk
• 0.60 and above — high risk

From your figures the tool also computes a half-height target (your height ÷ 2) and the signed gap to it, plus a healthy waist range for your height (0.40 to 0.49 × height). Every result is cross-checked a second way: instead of computing the ratio, the tool compares your waist directly against the height-scaled boundary waists (0.40, 0.50 and 0.60 × height). Both methods must agree before a band is shown.

WHtR's strength for Sri Lankan and other South Asian users is that the 0.50 boundary is the same for everyone, regardless of sex or ethnicity. Standard BMI cut-offs were calibrated mainly on European populations and can under-state body-fat risk for South Asian body types, so someone with a “normal” BMI can still carry risky central fat that WHtR catches. To measure your waist accurately, the WHO STEPS manual says to use the midpoint between your lowest rib and the top of your hip bone, taken at the end of a normal breath out. This is a screening aid only — it does not diagnose any condition, and you should see a doctor for personal medical advice.

• NICE Guideline NG246 — Obesity: identification, assessment and management (the ‘waist less than half your height’ rule)
• Ashwell M, Gibson S. BMJ Open 2016;6:e010159 — Waist-to-height ratio as an indicator of early health risk (band boundaries)
• WHO STEPS Surveillance Manual — physical measurements (waist-measurement technique)
• Sri Lanka Ministry of Health — NCD prevention (local context)

The boundaries and the 0.50 rule on this page were last cross-checked against NICE NG246 and Ashwell & Gibson (2016) on 2026-06-13. They are reviewed whenever the underlying guidance is updated.