Waist-to-height ratioWHtR
Waist circumference divided by height: arguably the best single-number risk screen.
Waist to height ratio is your waist circumference divided by your height, in the same units. The rule it produces is memorable: keep your waist under half your height.
It exists because BMI cannot see where weight sits, and where it sits is what carries the metabolic risk. Visceral fat inside the abdomen behaves differently from fat under the skin elsewhere, and a tape measure round the middle detects it far better than a weight and height calculation can.
The 0.5 boundary came from a systematic review that collated 78 studies published between 1950 and 2008, and found waist to height ratio and waist circumference predicted cardiovascular disease and diabetes more often than BMI did.
Its practical advantages are considerable. It needs one measurement and a number you already know, it requires no tables or age adjustments, the boundary is the same for men and women, and it works reasonably across populations where BMI thresholds differ.
It is not perfect. It cannot distinguish visceral from subcutaneous abdominal fat, it is affected by measurement technique, and it says nothing about muscle mass or fitness, both of which matter independently.
Measure it properly for it to mean anything: at the midpoint between the lowest rib and the top of the hip bone, tape parallel to the floor, at the end of a normal breath out, without holding your stomach in.
In practice, it is the single most informative measurement you can take at home with a tape. Our waist to height ratio calculator does the arithmetic and it belongs alongside blood pressure rather than alongside the scale.