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Waist To Height Ratio vs BMI
BMI relates weight to height; waist-to-height ratio relates waist size to height. They describe different aspects of body size and can be used together in adult assessment.
Updated 16 October 2026 • Tools by Layna Editorial Team • General information
Weight and waist are different measurements
BMI = weight (kg) ÷ height (m)². Waist-to-height ratio = waist circumference ÷ height, using the same length unit for both. BMI is expressed in kg/m²; waist-to-height ratio is dimensionless.
BMI is a broad height-and-weight screen. Waist-to-height ratio adds information about waist size relative to height. Neither is a direct measurement of body fat percentage or a stand-alone diagnosis.
Compare what goes into the result
| Feature | Waist-to-height ratio | BMI |
|---|---|---|
| Inputs | Waist circumference and height | Body weight and height |
| What changes it | A different waist or height measurement | A different weight or height measurement |
| Useful context | Waist size and central adiposity assessment | General body-size screening |
| Main limitation | Tape position and technique affect the result | Does not distinguish fat from muscle or show fat distribution |
Worked example: equal BMI, different waist ratio
Two hypothetical adults are each 170 cm tall and weigh 75 kg. Each has BMI 75 ÷ 1.70² = 26.0 kg/m² when rounded.
A waist of 80 cm gives 80 ÷ 170 = 0.47. A waist of 95 cm gives 95 ÷ 170 = 0.56. Their BMI is the same, but the waist measurement adds a difference that BMI cannot show.
Do not enter waist in centimetres and height in metres: 80 ÷ 1.70 would be the wrong calculation. Use 80 ÷ 170, or 0.80 ÷ 1.70.
Interpret the pair with the right scope
NICE recommends considering waist-to-height ratio alongside BMI in adults with BMI below 35 kg/m², as a practical estimate of central adiposity. Its general adult message is to keep the waist below half the height; that is a ratio below 0.5. A threshold is a screening aid, not a personal diagnosis.
For repeat measurements, follow the same technique. NICE describes measuring midway between the bottom of the ribs and top of the hips, after breathing out naturally. Do not switch between that point and the narrowest part of the waist and interpret the difference as body change.
Children need age-appropriate assessment, and pregnancy changes the usefulness of waist measures. Medical history and other clinical information remain relevant when interpreting adult screening results.
Use the relevant calculator
Frequently asked questions
Does a ratio of 0.5 mean 50% body fat?
No. It means waist circumference is half of height. It is not a fat-mass percentage.
Can I use inches instead of centimetres?
Yes, if both waist and height use inches. The ratio is unchanged when both inputs use the same unit.
Which is better if the two results differ?
They describe different measurements. Do not choose the more reassuring result; consider the appropriate scope and obtain clinical interpretation when needed.
Sources and method
The worked figures are illustrative arithmetic. The references below explain the underlying definitions and limits.