Waist-to-height ratioWHtR

Waist-to-height ratio divides waist circumference by height in the same units. The rule of thumb attached to it is memorable: keep your waist to less than half your height, so a ratio below 0.5.

It matters because it captures central adiposity while adjusting for body size, and it performs at least as well as BMI — often better — at predicting cardiometabolic risk across ages, sexes and ethnic groups. NICE guidance in the UK now recommends it alongside BMI for exactly that reason.

In practice it is easy to self-measure and needs no equipment beyond a tape. Its one weakness is the same as any tape measure: technique drift. Measure at the same landmark, at the end of a normal exhale, and compare like with like over time.