BMI sees total mass and height, and cannot tell where the mass is or what it is made of. That produces two distinct failures, in opposite directions — and only one of them ever gets discussed.
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Waist circumference divided by height, in the same units. A dimensionless ratio, so one set of boundaries for everyone: no separate chart by sex, no adjustment for age.
Keep your waist under half your height: WHtR < 0.5. At 175 cm that is under 88 cm; at 190 cm under 95. UK NICE guidance uses it alongside BMI.
Visceral fat packed around the organs carries far more risk than the same mass on hips and thighs. Waist is a crude, direct proxy; body mass counts muscle, bone and fat alike.
Midway between the lowest rib and the top of the hip bone, breathing out normally, tape snug on skin: not over a waistband, not holding your breath in.
Everyone knows the muscular athlete scored as overweight. Far more common, and far quieter, is normal-weight central obesity: a BMI of 24 with a 95 cm waist on a 180 cm frame. The first is a false alarm somebody laughs off; the second is a false reassurance nobody investigates.
A tape measure is cheap, portable and gives the same answer anywhere, while scales vary with hydration, time of day and what you last ate. Weight is the noisier measurement, and it is the one everyone tracks.
It cannot tell visceral from subcutaneous fat and knows nothing about blood pressure, lipids, glucose or fitness, all of which predict outcomes better than any body measurement. Being inside 0.5 is reassuring, not exonerating.
Midway between the bottom of your lowest rib and the top of your hip bone — roughly level with the navel for most people, though the landmarks matter more than the navel does. Directly on skin or over one thin layer, breathing out normally, tape snug but not compressing. Measuring over a waistband, or holding your breath in, is the commonest way to get a number that means nothing.
For predicting cardiometabolic risk in an individual, generally yes — and it takes one measurement rather than two. But it is still a proxy: it cannot distinguish visceral fat from subcutaneous, and it says nothing about fitness, blood pressure, lipids or blood glucose, all of which matter more than any body measurement.
Much less than BMI or raw waist circumference do, which is the main practical argument for it — a single 0.5 boundary works reasonably across sexes, ages above about 6, and ethnic groups where absolute waist thresholds need separate cut-offs. "Less adjustment" is not "none": some guidance uses lower boundaries for people of South Asian descent.
This page does not compute it, deliberately. It captures fat distribution rather than amount, which makes it informative but harder to use: it needs a second measurement, separate thresholds for men and women, and it can sit perfectly still while both numbers grow together. Waist-to-height needs one measurement and one boundary, which is most of why it is the more practical instrument.
An adult measuring accurately at the correct landmark. The 0.5 boundary is a general adult threshold, not a diagnosis, and a single number cannot describe anybody's health. Not modelled: age and sex-specific refinements, ethnicity-specific cut-offs, pregnancy, growth in children and adolescents, ascites or other conditions that change abdominal girth for reasons unrelated to fat, athletes with unusual trunk musculature, and every clinical measure — blood pressure, lipids, HbA1c, fitness — that predicts outcomes better than any tape measure.
This page has changed in 184 archived releases, but each of those was a site-wide pass, so none is attributable to this tool on its own and none is listed here. That is not a claim that the tool never changed — a release that reworked many pages at once may well have altered this one too. The changelog has them.