Adult BMI is weight in kilograms divided by height in metres squared. The result is the same under Chinese and WHO criteria, but the category can differ: Chinese adult overweight starts at BMI 24, while WHO uses 25. Select a standard before interpreting a result.
Use the adult BMI calculator for instant results, unit conversion, a reference weight interval and optional local records.
How to calculate BMI: a worked example
For a height of 175 cm and a weight of 70 kg, first convert height to metres: 175 ÷ 100 = 1.75. Then calculate 70 ÷ (1.75 × 1.75) = 22.857142… kg/m². The calculator displays 22.86 and uses the unrounded value for classification.
Do not square the height in centimetres without converting it. Entering 175 as metres or confusing 140 jin with 140 kg changes the calculation substantially.
Chinese adult BMI standards compared with WHO
| Category | Chinese adult standard | WHO adult standard |
|---|---|---|
| Underweight | < 18.5 | < 18.5 |
| Normal range | 18.5 ≤ BMI < 24 | 18.5 ≤ BMI < 25 |
| Overweight | 24 ≤ BMI < 28 | 25 ≤ BMI < 30 |
| Obesity | ≥ 28 | ≥ 30 |
For example, at 175 cm and 75 kg, BMI is approximately 24.49. This falls in the Chinese adult overweight category but the WHO normal interval. Neither calculation is wrong: the thresholds differ. A value exactly equal to a threshold enters the next category.
For WHO results, the calculator also distinguishes obesity class I (30 to below 35), class II (35 to below 40) and class III (40 or above). The Chinese comparison uses the general obesity threshold of 28.
Kilograms, jin, pounds and feet
This tool defines one jin as the mainland Chinese market jin: 500 g, or 0.5 kg. Thus 140 jin equals 70 kg. One pound is exactly 0.45359237 kg and one inch is exactly 2.54 cm. A foot contains 12 inches. Other regional definitions of jin are not used.
Switching units converts the measurement; it does not reinterpret 70 kg as 70 lb. Use the unit converter for other length and mass conversions.
How the reference weight interval is calculated
Multiply each normal BMI boundary by height in metres squared. At 1.75 m, the Chinese adult interval is 56.65625 kg to below 73.5 kg; the WHO interval is 56.65625 kg to below 76.5625 kg. Displayed bounds are rounded, so the inequality and selected standard matter.
This interval is not a personal ideal weight or a prescription to lose weight. The slider demonstrates the formula at a fixed height; it does not set a treatment goal or alter your saved measurement.
Who should not use this adult classification alone?
The tool is for adults aged 18 and over. Children and adolescents need growth references that consider age and sex; pregnancy needs separate assessment. High muscle mass, reduced muscle mass in older adults and fat distribution can also limit what BMI says about an individual.
BMI is not body-fat percentage and cannot diagnose a condition. Men and women share the same arithmetic formula and the adult cut-offs shown here. Discuss individual concerns with a qualified healthcare professional.
Privacy and local measurement history
Height and weight are calculated locally and are not added to analytics events or page URLs. Nothing is saved automatically. Clicking Save stores up to 90 measurements in this browser; you can remove one record, confirm deletion of all records or export a CSV. Shared-device users may see saved records.
History is not an account or cloud backup. Clearing browser site data deletes it. Exported files contain health information and should be kept private. Ordinary site analytics and technical requests are separate; see the privacy policy.
Sources and review
Reviewed November 3, 2026 by ToolKnit. This is an explanation of the tool and cited standards, not a clinical review or medical advice.
NHC: Dietary Guidelines for Adults with Obesity (2024), BMI classification