Waist-to-Height Ratio Calculator (NICE bands)

How it works

WHtR captures where fat sits, not just how much there is. Fat around the middle is more strongly linked to type 2 diabetes, high blood pressure, and heart disease than fat elsewhere, and because the measure divides by height it works across different body sizes, both sexes, and all ethnicities — which BMI doesn't do as well. NICE recommends it alongside BMI for adults with a BMI under 35 and sets three bands: 0.4–0.49 healthy, 0.5–0.59 increased central adiposity, and 0.6 or more high. The memorable version is the half-height rule: your waist should be less than half your height. This page also shows that half-height figure as a concrete waist target.

Worked example

Measure your waist at the midpoint between the bottom of your ribs and the top of your hip bones, then divide by your height in the same units. NICE's own example: 96.5 cm ÷ 170 cm = 0.57 — in the increased-risk band. For an 80 cm waist at 170 cm, the ratio is 80 ÷ 170 = 0.47, healthy, and half of 170 cm is 85 cm — the waist to stay under. The units cancel: the same body measured in inches (31.5 ÷ 66.9) gives the identical 0.47.

Frequently asked questions

How do I measure my waist correctly?

Around the midpoint between the bottom of your lowest rib and the top of your hip bone (roughly level with your belly button), with the tape snug but not compressing the skin, after breathing out normally. Don't measure over thick clothing. Consistency matters more than the exact spot — measure the same way each time to track change.

Why waist-to-height instead of BMI?

BMI uses total weight and can't tell muscle from fat or say where fat sits. Waist-to-height targets central fat, the kind most linked to metabolic disease, and needs no separate charts by sex or ethnicity — one boundary (0.5) applies to most adults. NICE recommends using it with BMI, not instead of it, for adults with a BMI below 35.

What does "keep your waist under half your height" mean?

It's the plain-language version of WHtR < 0.5: if your waist measurement is less than half your height, you're in the healthy band. It's easy to check without a calculator — a piece of string cut to your height, folded in half, should reach around your waist with slack. Above half, the ratio is 0.5 or more and risk starts to rise.

Is this valid for everyone?

NICE applies the bands to adults with a BMI under 35 of both sexes and all ethnicities, including people with high muscle mass. Above BMI 35 the ratio adds little (central obesity is already clear), and it's not used the same way for children — the NHS has a separate children's tool. Pregnancy also makes waist measures uninterpretable.

My ratio is below 0.4 — is that a problem?

It's below the range NICE labels healthy (0.4–0.49), meaning a very small waist relative to height. On its own that's usually not a concern, but a very low waist can accompany being underweight, which has its own risks. Look at it alongside BMI and overall health rather than treating a low ratio as automatically good.

Does a healthy ratio mean I'm healthy?

No — it's one screening measure. A ratio under 0.5 is reassuring for central-fat risk, but it says nothing about blood pressure, cholesterol, fitness, or blood sugar, which can be off regardless. Use it as one input among several, and see a clinician for anything that concerns you rather than relying on a single number.

How accurate is this, and what does it exclude?

The ratio is exact for the waist and height you enter; its usefulness depends on measuring the waist consistently and correctly. It's a screening tool, not a diagnosis, and it excludes muscle, overall fat, fat distribution beyond the waist, and every other health marker. It isn't validated for children or during pregnancy.