Waist ratio calculator
Work out waist-to-hip and waist-to-height ratios and compare them with WHO and NICE thresholds.
A clear answer. Here’s how.
Waist-to-hip ratio = waist ÷ hip, and waist-to-height ratio = waist ÷ height, both in the same unit. The WHO expert consultation (2008) treats a waist-to-hip ratio above 0.90 for men or 0.85 for women as abdominal obesity, and a waist circumference of 94 cm (men) or 80 cm (women) as increased risk and 102 cm or 88 cm as substantially increased risk. NICE’s obesity guidance uses waist-to-height bands: below 0.4 take care, 0.4–0.49 lower risk, 0.5–0.59 increased risk, 0.6 or more high risk. The bands use the unrounded ratio.
How this is checked
3 reference checks passed These 3 cases were run when this page was built, on 20 October 2026, and all reproduce within the stated tolerance. The same cases are part of the automated tests that run on every change to Toolmoz. Engine version 1.
See the checks and where each expected answer comes from
Case 1
- Inputs
- Sex used by the equation maleMeasurement units metricWaist circumference (cm, or inches) 85Hip circumference (cm, or inches) 98Height (cm, or inches) 180
- Expected, and what Toolmoz gave
- Waist-to-hip ratio expected 0.8673, Toolmoz 0.8673469387755102Waist-to-height ratio expected 0.4722, Toolmoz 0.4722222222222222Waist-to-hip result expected At or below the WHO threshold, Toolmoz At or below the WHO threshold
- Where the expected answer comes from
- 85 ÷ 98 = 0.86735 and 85 ÷ 180 = 0.47222, against the WHO men’s threshold of 0.90 (hand calculation)
- Allowed difference
- ±0.0001
Case 2
- Inputs
- Sex used by the equation femaleMeasurement units metricWaist circumference (cm, or inches) 90Hip circumference (cm, or inches) 100Height (cm, or inches) 150
- Expected, and what Toolmoz gave
- Waist-to-hip ratio expected 0.9, Toolmoz 0.9Waist-to-height ratio expected 0.6, Toolmoz 0.6Waist-to-hip result expected Above the WHO threshold, Toolmoz Above the WHO thresholdWHO waist circumference result expected Substantially increased risk (at or above 88 cm), Toolmoz Substantially increased risk (at or above 88 cm)
- Where the expected answer comes from
- 90 ÷ 100 = 0.9 against the women’s threshold 0.85, 90 ÷ 150 = 0.6, and 90 cm is at least 88 cm (hand calculation)
- Allowed difference
- ±1e-9
Case 3
- Inputs
- Sex used by the equation maleMeasurement units imperialWaist circumference (cm, or inches) 34Hip circumference (cm, or inches) 40Height (cm, or inches) 70
- Expected, and what Toolmoz gave
- Waist-to-hip ratio expected 0.85, Toolmoz 0.8500000000000001Waist-to-height ratio expected 0.4857, Toolmoz 0.48571428571428565Waist circumference (cm) expected 86.36, Toolmoz 86.36
- Where the expected answer comes from
- 34 ÷ 40 = 0.85, 34 ÷ 70 = 0.48571 and 34 in × 2.54 = 86.36 cm, shown to one decimal (exact inch definition)
- Allowed difference
- ±0.0001
What this shows: the engine reproduces independently worked values for these cases. It does not prove every possible input is right. To test an answer you were given, see how to check a number; to see what is and is not checked across Toolmoz, see the accuracy ledger.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Sex used by the equation
- Male
- Measurement units
- Metric (cm, kg)
- Waist circumference (cm, or inches)
- 85
- Hip circumference (cm, or inches)
- 98
- Height (cm, or inches)
- 180
Example result
- Waist-to-hip ratio
- 0.8673
- WHO waist-to-hip threshold for abdominal obesity
- above 0.90
- Waist-to-hip result
- At or below the WHO threshold
- Waist circumference (cm)
- 85.0
- WHO waist circumference result
- Below the increased-risk level (under 94 cm)
- Waist-to-height ratio
- 0.4722
- Waist-to-height band (NICE)
- 0.4 to 0.49: lower health risk
Screening ratios, not a diagnosis. WHO cut-offs were set for adults of European origin and apply to adults only; NICE uses the waist-to-height ratio alongside BMI. Measure at the midpoint between the lowest rib and the top of the hip bone, and at the widest part of the hips.