About this tool
The Waist-to-Height Ratio Calculator is a free, in-browser tool that divides your waist circumference by your height and places the result in the standard risk bands. The widely cited rule of thumb — endorsed by the UK's NICE guidance in 2022 — is to keep your waist below half your height, i.e. a ratio under 0.5.
Because it captures central (abdominal) fat, waist-to-height ratio predicts cardiometabolic risk better than BMI for many people, and the same 0.5 threshold works across sexes and most adult heights. The ratio is unit-free: measure waist and height in the same unit and the math runs instantly in your browser.
Frequently asked questions
How do I measure my waist correctly?
Measure midway between the bottom of your ribs and the top of your hips (roughly at the navel), after breathing out normally, with the tape snug but not compressing the skin.
What do the bands mean?
Below 0.4 is slim (possibly underweight), 0.4–0.49 healthy central fat, 0.5–0.59 increased risk, and 0.6 or above high risk of cardiometabolic disease — the bands used in NICE's 2022 guidance.
Why use this instead of BMI?
BMI cannot tell muscle from abdominal fat. Waist-to-height ratio targets central fat, which drives metabolic risk, so a muscular person is not misclassified and a normal-BMI person with belly fat is flagged.
Do the units matter?
No — the ratio is dimensionless, so cm/cm and in/in give the identical result. Just measure both values in the same unit. Everything is computed locally; nothing is uploaded.