Waist-to-Hip Ratio Calculator

What the waist-to-hip ratio tells you

Two people with the same weight and the same BMI can carry their fat very differently. Fat stored deep inside the abdomen, around the organs, is linked more closely with type 2 diabetes and heart disease than fat stored under the skin of the hips and thighs. The waist-to-hip ratio compares the two circumferences, so a higher number means more of your size sits around your middle.

That is the difference from the neighbouring calculators. BMI measures how heavy you are for your height, and the body fat calculator estimates how much of that weight is fat. Neither says where the fat is. This calculator does, and it shows three related numbers:

• Waist-to-hip ratio, compared with the WHO cut-off points summarised in the report of the 2008 WHO expert consultation on waist circumference and waist-to-hip ratio: 0.90 for men and 0.85 for women. At or above them, the risk of metabolic complications is described as substantially increased.
• Waist circumference on its own, compared with the levels in the same table: above 94 cm (37 in) for men or 80 cm (31.5 in) for women is increased risk, above 102 cm (40.2 in) or 88 cm (34.6 in) is substantially increased.
• Waist-to-height ratio, if you enter your height, classified with the bands used by NICE in England.

The ratio is shown and classified to two decimal places, so the label always matches the number you see.

How to measure your waist and hips

The WHO consultation recommends one standard method. Measuring the same way each time also makes your results comparable over time:

1. Stand upright with your feet close together, arms relaxed at your sides and your weight on both feet. Wear little or no clothing over the area.
2. Waist: find the bottom of your lowest rib and the top of your hip bone (the iliac crest) at your side. Place the tape halfway between them, level with the floor. Measure at the end of a normal breath out, without pulling your stomach in.
3. Hips: measure around the widest part of your buttocks, again keeping the tape level.
4. Use a tape that doesn’t stretch, snug against the skin but not pressing in.
5. Take each measurement twice. If the two are within 1 cm (about ⅜ in) of each other, use the average; if not, measure twice more.

The waist point is not the same as your belly button or your trouser waistband, and measuring there can give a noticeably different number. The ratio has no units, so inches and centimetres give the same answer as long as both measurements use the same one.

Formulas

waist

circumference midway between the lowest rib and the top of the hip bone

hip

circumference at the widest part of the buttocks

height

standing height, in the same unit as the waist

Turning the formulas around gives two useful targets. The waist at which your ratio reaches the WHO cut-off is hip × 0.90 for men or hip × 0.85 for women. NICE’s advice, “keep your waist to less than half your height”, is the waist-to-height ratio of 0.5 written as a measurement: height ÷ 2.

NICE guideline NG246 classifies waist-to-height ratio in adults as 0.40–0.49 healthy, 0.50–0.59 increased health risk and 0.60 or more further increased risk, for both sexes and all ethnic groups, in people with a BMI under 35.

Worked examples

A man who is 5 ft 10 in (70 in) tall, with a 34 in waist and 39 in hips:

1. Waist-to-hip ratio: 34 ÷ 39 = 0.8718, shown as 0.87, below the 0.90 cut-off for men.
2. Waist: 34 in = 86.4 cm, not above the 94 cm level.
3. Waist-to-height ratio: 34 ÷ 70 = 0.4857, shown as 0.49, in the healthy band.
4. His ratio would reach 0.90 at a waist of 39 × 0.90 = 35.1 in; half his height is 35 in.

A woman who is 5 ft 4 in (64 in) tall, with a 35 in waist and 40 in hips:

1. Waist-to-hip ratio: 35 ÷ 40 = 0.875, shown as 0.88, at or above the 0.85 cut-off for women.
2. Waist: 35 in = 88.9 cm, above the 88 cm level for substantially increased risk.
3. Waist-to-height ratio: 35 ÷ 64 = 0.5469, shown as 0.55, in the increased-risk band.
4. At 40 in hips, a 34 in waist (40 × 0.85) would bring her ratio to the cut-off; half her height is 32 in.

Limits of these numbers

• Hips change the ratio too. Losing fat from the hips, or building muscle there, moves the ratio even if your waist stays the same. That is one reason the WHO consultation found waist circumference easier to use, and why this calculator shows your waist and waist-to-height ratio alongside.
• The waist levels come from one population. The report notes that the 94/80 cm and 102/88 cm values were based on a Dutch study of white European adults and were given as an example rather than a formal recommendation. The International Diabetes Federation uses lower waist levels for men of South Asian, Chinese and Japanese origin (90 cm).
• Not for children or pregnancy. The WHO cut-offs are for adults. NICE has its own guidance on waist-to-height ratio for children aged 5 and over; during pregnancy these measures don’t apply.
• Measurement error. A centimetre or two in either measurement can move the ratio by 0.01 to 0.02, enough to cross a cut-off. Measure twice and use the average.