Waist-to-Height Ratio Calculator

Choose Centimeters in the units control, then enter a waist circumference of 90 and a height of 175. The inches and centimetres fields keep separate values, so switching units does not convert a number you have already typed.

The results panel shows a waist-to-height ratio of 0.514, the screening category Increased risk, and 103% of the 0.5 threshold. That last line is the same ratio restated as a percentage of the 0.5 line: 100% is exactly half your height, and anything above 100% is over it.

To turn the result into a target, halve your height. At 175 cm, half is 87.5 cm, so this waist is 2.5 cm above the line. At 5 ft 8 in (68 inches), half is 34 inches. The target changes only with height, which is why the same waist can be healthy on one person and not on another.

Ratio = waist circumference ÷ height, shown to three decimal places. Because both measurements share a unit, the unit cancels: 90 cm ÷ 175 cm and 35.4 in ÷ 68.9 in describe the same body.

Percent of threshold = (ratio ÷ 0.5) × 100, shown as a whole number.

Category rule, applied to the unrounded ratio: below 0.4 is Below typical range; 0.4 up to but not including 0.5 is Healthy range; 0.5 up to but not including 0.6 is Increased risk; 0.6 and above is High risk. The three upper bands match the NICE NG246 classification.

Height is floored at 1 and waist at 0 to avoid dividing by zero; neither limit affects a real measurement.

The boundaries are sharp in the code but not in biology. A ratio of 0.49 and a ratio of 0.51 carry almost the same risk, and a one-centimetre difference in where the tape sits moves the ratio at 175 cm by about 0.006. For example, 89 cm gives 0.509 and 91 cm gives 0.520.

Switch to Inches and enter a 34-inch waist with a height of 68 inches. The ratio is 0.500, the category is Increased risk, and the threshold line reads 100%. Exactly half your height is not less than half, so it lands in the increased band.

Keep the waist at 34 inches and change only the height. At 72 inches (6 ft) the ratio falls to 0.472, Healthy range, 94% of the threshold. At 64 inches (5 ft 4 in) it rises to 0.531, Increased risk, 106%. One waist measurement falls in two different bands across an eight-inch height difference, which is the whole point of dividing by height. A fixed waist cut-off cannot make that adjustment.

At the top of the scale, a 110 cm waist at 175 cm gives 0.629 and 126% of the threshold, in the High risk band. Here the waist is more than 60% of height, the level NICE describes as further increased health risk.

Waist circumference is only comparable with the NICE bands if it is measured the same way. The protocol used by NICE and by the 2008 World Health Organization Expert Consultation on waist circumference is:

• Stand upright with your feet together and your abdomen relaxed, with the tape against bare skin or thin clothing.
• Find the bottom of your lowest rib and the top of your hip bone (the iliac crest) on one side.
• Wrap the tape around your middle halfway between those two points, keeping it level all the way round.
• Read the tape at the end of a normal breath out, snug against the skin but not pressing in.
• Measure twice, and use the average if the two readings differ.

This midpoint is usually above the waistband of your trousers and is not always the narrowest point of your torso. Some quick guides suggest the narrowest point or the navel instead. For comparison with NICE's cut-offs, use the midpoint and then stay consistent. Measure height barefoot, standing against a wall, in the same unit as the waist.

BMI relates weight to height and cannot tell where fat is stored. Fat carried centrally, around the abdominal organs, is more closely tied to type 2 diabetes, hypertension and cardiovascular disease, and waist circumference tracks it better than weight does. Two adults who are both 175 cm and share the same BMI could have waists of 80 cm and 100 cm. Their ratios would be 0.457 and 0.571, in different NICE bands.

The strongest summary of the evidence is a meta-analysis by Ashwell, Gunn and Gibson in Obesity Reviews (2012). It pooled 31 studies and compared how well each measure picked out adults with diabetes, high blood pressure, abnormal lipids and cardiovascular disease. Average areas under the ROC curve were 0.704 for waist-to-height ratio, 0.693 for waist circumference and 0.671 for BMI. The margin is modest, but the ratio came out ahead, and it needs only a tape measure.

NICE's 2025 guideline NG246 recommends that adults with a BMI below 35 measure and use their waist-to-height ratio as well as BMI, not instead of it. NICE states that the same bands apply to both sexes and all ethnicities, and to adults with high muscle mass, groups for whom BMI cut-offs are often adjusted or less reliable. Its waist-to-height recommendation for adults covers people with a BMI below 35.

This calculator does not diagnose obesity, metabolic disease or cardiovascular risk. It divides one measurement by another. It cannot see blood pressure, blood glucose, cholesterol, family history, smoking or fitness, all of which a clinician weighs alongside it.

The NICE bands are for adults. They do not apply during pregnancy, when waist size changes for reasons unrelated to fat. NICE does use the ratio for children and young people aged 5 and over, but body proportions change through growth, and this page is written for adults; a child's or teenager's result should be interpreted by a health professional. Abdominal swelling from bloating, fluid or a medical condition will also inflate the ratio.

The 'Below typical range' label under 0.4 is not a NICE category, and a low ratio does not by itself mean anything is wrong. If it comes with a low BMI or unintended weight loss, that is worth discussing with a clinician.

Measurement technique matters more than the arithmetic. A tape a few centimetres off the midpoint, held loosely or read after a big meal, can move you across a band boundary.

Because NICE recommends reading this ratio alongside BMI rather than instead of it, the natural next step is the BMI calculator, which gives the standard weight-for-height category. If you want an estimate of how much of your weight is fat, the body fat calculator uses waist, neck and height measurements, including the same waist you just took. The ideal weight calculator shows a height-based weight range from several published formulas. Central fat often travels with low HDL and raised triglycerides, so if you have a recent lipid panel the cholesterol ratio calculator is a useful companion. The waist-to-hip ratio calculator is the sister measure: it compares the waist with the hips rather than with height, and reads the result against the WHO's separate thresholds for men and women. The guide to where BMI and body fat percentage disagree explains why a single measure can mislead.