BMI Guide: Chinese 24/28 vs WHO 25/30
BMI is weight in kilograms divided by height in metres squared. On the Chinese adult scale, below 18.5 is underweight, 18.5 to 23.9 is normal, 24 to 27.9 is overweight and 28 or above is obese; the WHO scale puts overweight at 25 and obesity at 30.
When BMI is enough
If the only numbers you have are height and weight, BMI is the cheapest first check. It needs no equipment and no body-fat measurement, and it maps onto population data, which is why public-health screening has used it for decades. It also works as a trend while you lose weight: weigh at the same time each week and watch the direction.
It stops being enough as soon as you need to know how much to lose, whether you have enough muscle, or where the fat sits. BMI describes only the ratio of weight to height; it cannot separate muscle, fat, water and bone.
Calculating and interpreting it correctly
The formula is kilograms divided by metres squared. If you have centimetres, divide by 100 first. Someone at 173 cm and 68.5 kg comes out at 68.5 ÷ 1.73 ÷ 1.73, about 22.9, inside the normal band. This is the most common error: feeding centimetres into a formula that expects metres produces an absurdly small result.
The second trap is rounding before you classify. 23.96 and 24.0 are close, but the second crosses the Chinese overweight line and flips the conclusion. Compare the unrounded value against the threshold. Third, do not mix the scales: 24.0 to 24.9 is overweight in China and still normal under WHO.
- Chinese adult scale: below 18.5 underweight | 18.5–23.9 normal | 24–27.9 overweight | 28+ obese
- WHO scale: below 18.5 underweight | 18.5–24.9 normal | 25–29.9 overweight | 30+ obese
- Measure at the same time and state — morning, fasted, after the bathroom, similar clothing — or the trend means nothing
- Watch the direction over weeks; a 1–2 kg swing within a week is normal
Limits: it measures weight, not health
BMI cannot tell muscle from fat. A regular lifter can sit at 27 with low body fat; someone with a normal BMI but little muscle and visceral fat can carry real metabolic risk. Age matters too: muscle mass falls with age, so the same BMI implies a higher fat share. The adult bands do not apply to pregnant women, children or athletes.
Treat BMI as a first filter, not a verdict. For a better picture add waist circumference — central obesity is an independent risk marker, though cut-offs differ slightly between guidelines — plus body-fat percentage and blood pressure, lipids and glucose. If you are losing weight, track fat and waist rather than the single number on the scale.
FAQ
Why are the Chinese BMI cut-offs different from the WHO ones?
Body-fat distribution differs between populations. At the same BMI, Asian populations tend to carry a higher body-fat percentage and more central obesity, and metabolic risk such as diabetes and hypertension rises at a lower BMI. The Chinese adult standard therefore moves the overweight line from 25 down to 24 and obesity from 30 down to 28. Both are right for their populations; a Chinese medical report usually uses 24 and 28.
What BMI is considered normal?
For Chinese adults, 18.5 to 23.9 is normal, 24 to 27.9 is overweight, 28 and above is obese, and below 18.5 is underweight. Under the WHO scale, 18.5 to 24.9 is normal, 25 to 29.9 overweight, 30 and above obese. Anyone between 24 and 24.9 gets two different answers depending on the scale.
Is BMI wrong for muscular people?
For that individual, yes. BMI only compares weight with height, and muscle is dense, so trained people are routinely overestimated. Body-fat percentage and waist circumference describe them better. BMI earns its keep in population screening, not in precise individual assessment.
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