What is BMI (body mass index)?
BMI is weight (kg) divided by height (m) squared — a simple indicator for estimating body fat.
BMI = weight (kg) ÷ height (m)²
Korean criteria (Korean Society for the Study of Obesity)
| BMI | Category |
|---|---|
| Under 18.5 | Underweight |
| 18.5 ~ 22.9 | Normal |
| 23 ~ 24.9 | Pre-obese (overweight) |
| 25 ~ 29.9 | Class 1 obesity |
| 30 ~ 34.9 | Class 2 obesity |
| 35 or more | Class 3 obesity (severe) |
Asians tend to have a higher body fat percentage at the same BMI, so lower cutoffs are used than the WHO standard (25+ overweight).
Limits of BMI
BMI can't tell muscle from fat. People with a lot of muscle may get a high BMI, so it's best read together with waist size (90cm+ for men or 85cm+ for women indicates abdominal obesity).
FAQ
Is BMI used for children too?
For ages 18 and under, percentiles on growth charts by sex and age are used, so these criteria shouldn't be applied as is.