By the Tooliday Team. Last updated 14 November 2026.
BMI uses only height and weight, so it cannot tell where on the body weight is carried. Fat stored around the waist is linked with more health risk than fat stored elsewhere, which is why many health guides suggest a waist measurement as an extra check. One simple way is the waist-to-height ratio. You can also calculate your BMI with our BMI Calculator and compare the two.
How to measure your waist
- Stand up straight and relax your stomach.
- Find the point halfway between the bottom of your lowest rib and the top of your hip bone.
- Wrap a tape measure around your waist at that point, level with the floor, snug but not squeezing.
- Breathe out normally and read the measurement, in the same units as your height.
Measure against bare skin or a thin layer of clothing, and do not pull the tape tight.
The calculation
Waist-to-height ratio = waist ÷ height
Use the same units for both. Example: a person who is 170 cm tall with an 80 cm waist has a ratio of 80 ÷ 170 = 0.47. Another person of the same height with a 90 cm waist has a ratio of 90 ÷ 170 = 0.53.
What the number suggests
A commonly quoted rule of thumb is to keep your waist to less than half your height, which means a ratio under 0.5. Guidance in the UK from the National Institute for Health and Care Excellence describes a ratio of 0.4 to 0.49 as healthy, 0.5 to 0.59 as increased health risk and 0.6 or more as high risk for adults. These are guides for screening, not a diagnosis.
| Ratio | General guide |
|---|---|
| Below 0.4 | Very low, which may mean being underweight |
| 0.4 to 0.49 | Usually considered healthy |
| 0.5 to 0.59 | Increased risk |
| 0.6 and above | High risk |
Why it is used with BMI
Two people can have the same BMI but carry fat in different places. The waist-to-height ratio helps catch people whose BMI looks acceptable but who carry extra fat around the middle. It also needs no table of age or sex groups, which makes it simple to use. It is still only one measure, and it is not designed for children, people who are pregnant or those with some medical conditions.
What to do with the result
- Measure again in a few weeks the same way and compare, since one reading can vary.
- Look at it together with other things such as activity, eating habits, family history and blood tests that a doctor can arrange.
- If your ratio or your BMI worries you, talk to a doctor. Do not make big changes to your diet on the basis of a single number.
For more on BMI, read How to Calculate BMI and How to Measure Your Height and Weight Accurately for BMI.
This article is for general information and is not medical advice. It does not diagnose or treat any condition. Please consult a qualified healthcare professional about your health.