Waist-to-Height Ratio Calculator

A healthy waist-to-height ratio is 0.4–0.49 under UK NICE guidance — the simple rule is to keep your waist to less than half your height, a ratio under 0.5.

If you would rather look up a target waist than calculate a ratio, the waist-to-height ratio chart gives the measurement each threshold works out to at every height from 5′0″ to 6′4″, in centimetres and inches.

Why waist-to-height ratio matters

Waist-to-height ratio (WHtR) divides your waist measurement by your height. Because it tracks the fat stored around your middle — the kind most strongly linked to type 2 diabetes and heart disease — it often flags risk that a normal BMI can miss. The guidance rule is memorably simple: keep your waist to less than half your height, a ratio under 0.5. Since it's a ratio of two lengths, the units cancel — centimetres or inches give the same number.

UK NICE guidance (NG246) recommends using WHtR alongside BMI as a screening measure of central adiposity for adults with a BMI under 35, with the same bands for men and women and across ethnic groups. It pairs naturally with your waist-to-hip ratio and body fat percentage for a fuller picture of body composition.

Waist-to-height ratio bands (NICE)

Bands from NICE guideline NG246 (first introduced in the September 2022 update to CG189). The same bands apply to men and women, all ethnic groups, adults with BMI under 35, and children aged 5+.

The 40-inch rule and the half-height rule do not agree

Three common screens, three blind spots. BMI compares weight to height, so it cannot see where the fat sits. The fixed waist rule — a waist over 40 inches for men or over 35 inches for women, from the NIH NHLBI — has no height term in it at all, so it reads the same on a 5′2″ frame as on a 6′2″ one. Waist-to-height ratio has no sex term, so it draws one line for everyone. The last two are judging the same tape reading, and they disagree about it more often than they agree.

Where the fixed waist rule lands on the ratio scale

Ratios as this calculator prints them — waist divided by height, rounded to two places, then banded. Fixed 40 in / 35 in thresholds from NHLBI; the 0.50 line from NICE NG246.

Take a man of 5′6″ with a 38-inch waist. His ratio is 0.58 — increased central adiposity, and 12.7 cm over half his height — but 38 inches is under the 40-inch line, so the fixed rule clears him. He has to reach 40 inches to trip it, and by then his ratio is 0.61, in the high band. At 5′7″ and under, a 40-inch waist already reads as high central adiposity. Now the reverse: a woman of 6′0″ with a 35.5-inch waist is over the 35-inch line, yet her ratio is 0.49 — healthy, and 1.3 cm under half her height. The two rules coincide at exactly one height each: 5′10″ for women, because 35 inches is half of 70, and 6′8″ for men, which is above almost every adult male height. That is the arithmetic reason the two rules diverge, and it is consistent with the pooled finding cited on this page, that waist-to-height ratio screens better than waist circumference alone.

What is the second decimal place worth? One hundredth of ratio is your height divided by 100, in centimetres of waist: 1.57 cm at 5′2″, 1.78 cm at 5′10″, 1.88 cm at 6′2″. And because the calculator rounds to two places before it picks a band, at 5′10″ a waist of 88.0 cm still reads 0.49 and healthy while 88.1 cm reads 0.50 and increased — even though half his height is 88.9 cm, still 0.8 cm further on. The label turns a shade before the literal half-height mark. That is why the tool also prints your waist against half your height in plain centimetres: the gap moves smoothly where the band name jumps.

Measuring well, and the limits to know

Technique matters more than the decimal: measure midway between the bottom of your ribs and the top of your hips, after breathing out naturally, with the tape level and snug. WHtR is not meaningful during pregnancy, and above a BMI of 35 the waist measurement itself becomes unreliable, so NICE limits its use there. A ratio just over a boundary is a nudge to look at habits and trends — not a diagnosis. To turn the result into action, estimate your daily calories or check your healthy weight range.

Sources: NICE guideline NG246 — identifying and assessing overweight, obesity and central adiposity; Ashwell & Gibson, BMC Medicine (2014); Browning, Hsieh & Ashwell, Nutrition Research Reviews (2010); NHS waist-to-height guidance; NIH NHLBI — Assessing your weight and health risk (the 40-inch / 35-inch waist thresholds). Educational estimates, not medical advice.