Waist to Height Ratio Calculator

Divide your waist measurement by your height, both in the same unit. NICE’s own examples: 38 inches ÷ 67 inches ≈ 0.57, and 96.5 cm ÷ 170 cm ≈ 0.57. The ratio has no unit, so centimetres and inches give the same answer as long as both measurements use the same one. The calculator divides exactly, shows the ratio to two decimals as NICE does (with more places where two would round onto a band start or onto 0), and shows the working.

Either, as long as both are the same. If you know your height in feet and inches, convert it to inches: 5 feet 10 inches is 5 × 12 + 10 = 70 inches. On a computer you can type 5′10″ into the height box and the calculator reads it as 70 inches; on a phone, type 70. If you type a unit in both boxes and they differ (86 cm against 34 in), the calculator shows the conversion instead of an answer.

NICE, which writes the guidance used by the NHS in England, classifies an adult’s ratio like this: 0.4 to 0.49 is “healthy central adiposity”, “indicating no increased health risks”; 0.5 to 0.59 is “increased central adiposity”, “indicating increased health risks”; and 0.6 or more is “high central adiposity”, “indicating further increased health risks”. It advises keeping “their waist to less than half their height (so a waist-to-height ratio of under 0.5)”. The NHS says the same: “You should try to keep your waist size to less than half your height.”

0.5 is where NICE’s “increased” band starts: a waist exactly half your height is 0.50, which NICE classifies as increased central adiposity (0.5 to 0.59). Below 0.5, down to 0.4, is NICE’s healthy band. For a height of 170 cm, 0.5 is a waist of 85 cm; for 5′10″ (70 inches), 35 inches. NICE writes its bands to two decimals, so a ratio such as 0.4975 is 0.50 to two decimals: the calculator then shows 0.498 and says that to two decimals it is the start of the increased band.

No. NICE says its classification “can be used for people with a BMI under 35 kg/m² of both sexes and all ethnicities, including adults with high muscle mass.” The same bands apply to men and women, so the calculator asks for neither sex nor ethnicity. Some sites quote other cut-offs for particular groups; this page follows NICE.

NICE’s instructions: “Find the bottom of the ribs and the top of the hips. Wrap a tape measure around the waist midway between these points (this will be just above the belly button) and breathe out naturally before taking the measurement.” Measure your height in the same unit.

NICE does not ask you to choose. For adults with a BMI below 35, it recommends measuring the waist-to-height ratio “as well as their BMI, as a practical estimate of central adiposity”, to help assess and predict health risks. BMI uses your weight; the waist-to-height ratio looks at the waist, where central fat is carried. NICE’s bands are for people with a BMI under 35.

NICE’s healthy band starts at 0.4 and NICE gives no band below it, so the calculator says “under 0.4” rather than giving a label. Some online charts add a band below 0.4; it is not a NICE classification. A very low figure can also mean the two measurements are in different units (a waist in inches against a height in centimetres), and the calculator flags the lowest ratios as a likely unit mix-up. If you are worried about your weight, talk to a GP or another clinician.

NICE uses the same three bands for children and young people aged 5 and over (recommendation 1.10.10). The NHS calculator says not to use it if the person is under 5 years old, if you are pregnant, if you have been diagnosed with an eating disorder or think you may have one, if you have a growth disorder or any other condition that affects your height, or (for adults) if your BMI is over 35; for 5 to 17-year-olds it asks parents and carers to check BMI first.