A simple rule: keep your waist under half your height
The waist-to-height ratio (WHtR) divides your waist circumference by your height. It estimates abdominal fat, the fat around the organs that is most linked to heart disease, type 2 diabetes and high blood pressure. Many studies find it predicts these risks better than BMI, and it works with any unit, for adults of any height, sex or ethnic background. The message fits in a few words: keep your waist to less than half your height.
The formula and thresholds
WHtR = waist ÷ height, both in the same unit.
| Ratio | Meaning |
|---|---|
| Below 0.4 | Low: check that you are not underweight |
| 0.4 to 0.49 | Healthy |
| 0.5 to 0.59 | Increased risk |
| 0.6 or more | High risk |
The UK’s National Institute for Health and Care Excellence (NICE) adopted these thresholds in 2022 alongside BMI.
Worked example: waist 34 in, height 5 ft 9 in
- Height: 5 ft 9 in = 69 in.
- Ratio: 34 ÷ 69 = 0.49, just inside the healthy range.
- Maximum healthy waist: 69 ÷ 2 = 34.5 in.
Ratio at other waist sizes (height 69 in)
| Waist | Ratio | Above the target |
|---|---|---|
| 30 in | 0.43 | 0 |
| 34 in | 0.49 | 0 |
| 36 in | 0.52 | 1.5 in |
| 40 in | 0.58 | 5.5 in |
| 44 in | 0.64 | 9.5 in |
How to measure your waist
- Stand straight, feet together, and breathe out normally.
- Find the bottom of your lowest rib and the top of your hip bone; the waist is halfway between.
- Wrap a tape measure around, horizontal and snug without squeezing.
- Measure twice and take the average. Your belt size is not a good guide: trousers often sit below the waist.
WHtR, BMI and waist-to-hip ratio
BMI does not tell muscle from fat, nor where fat is stored. Two people with a BMI of 27 can have very different health risks if one carries weight on the hips and the other on the belly. The waist-to-hip ratio also measures fat distribution, but it needs two measurements and sex-specific thresholds. WHtR is the simplest of the three to use and to remember.
Reducing your waist
Abdominal fat responds well to a combination of regular physical activity, fewer ultra-processed foods and sugary drinks, enough sleep and less alcohol. Losing just 2 inches of waist measurably lowers blood pressure and blood sugar in most people.