Waist to height ratio
Divide your waist by your height. NICE adopted this in 2022 because it needs no chart and no calculator — keep your waist under half your height. Nothing you type here leaves your browser — it is worked out on your own device, so there is nothing to send and nothing to log.
This is arithmetic, not medical advice. These bands are NICE guidance from October 2022 for adults with a BMI under 35. A number is a reason to talk to a GP or practice nurse, not a diagnosis, and where you put the tape moves it more than the arithmetic does.
Keep your waist under half your height
That is the whole rule, and it is the reason NICE adopted this measure in 2022: it needs no chart, no lookup and no arithmetic. Divide your height by two. If your waist is under that, you are in NICE's healthy band.
| 0.4 to 0.49 | Healthy. No increased risk on this measure. |
|---|---|
| 0.5 to 0.59 | Increased central adiposity. Increased health risk. |
| 0.6 and over | High central adiposity. Further increased risk. Worth a conversation with a GP. |
NICE applies these to adults with a BMI under 35, across all sexes and ethnicities, and has extended them to children aged five and over. Checked against NICE on 21 September 2026.
The units cancel, which is the point
A ratio has no units. Measure in centimetres or in inches — as long as you use the same one for both — and the answer is identical. That is what makes it a rule you can apply with a tape measure and no calculator, and it is why it survives translation between countries where BMI charts do not.
Why not just BMI?
BMI is weight divided by height squared, and it cannot tell muscle from fat or say where the fat is. A heavily built athlete and a sedentary person of the same weight and height get the same BMI. And fat around the middle carries a different risk from fat elsewhere, which is the thing BMI is blindest to.
Waist-to-height addresses exactly that second gap. It does not replace BMI — NICE uses both, and says to use BMI alone above 35, where the waist measurement stops adding information. The BMI calculator is on this site too, with its own list of what it cannot see.
Where to put the tape
This matters more than the arithmetic. NICE means the midpoint between the bottom of your ribs and the top of your hip bone — usually roughly level with the navel, but find the bones rather than guessing. Measure against skin, standing, breathing out normally, with the tape snug and not pulled tight.
Two centimetres higher or lower moves the answer by about 0.01, and breathing in moves it by more than that. Measure it the same way every time and the trend is what is useful.
It is a prompt, not a diagnosis
A number over 0.5 does not mean you are ill, and a number under it does not mean you are well. NICE's own framing is that it is a reason to talk to somebody, alongside everything a single measurement cannot see: blood pressure, family history, what you eat, whether you move, and how you are actually doing.
What it will not do
- It will not apply to pregnancy, where the measurement means nothing.
- It will not apply to adults with a BMI of 35 or over, where NICE says to use BMI alone.
- It will not replace a conversation with a GP or practice nurse.