What Is BMI?
Body Mass Index (BMI) is a number calculated from your height and weight. Developed in the 19th century by Belgian mathematician Adolphe Quetelet, it became the WHO’s recommended screening tool for assessing adult weight status.
The BMI Formula
BMI = Weight (kg) ÷ Height (m)²
Example: Height 170cm (1.70m), Weight 65kg
BMI = 65 ÷ (1.70)² = 65 ÷ 2.89 = 22.5
BMI Classification: WHO vs. Asian Standard
| Category | WHO Standard | Asian Standard |
|---|---|---|
| Underweight | Below 18.5 | Below 18.5 |
| Normal | 18.5 – 24.9 | 18.5 – 22.9 |
| Overweight | 25.0 – 29.9 | 23.0 – 24.9 |
| Obese Class I | 30.0 – 34.9 | 25.0 – 29.9 |
| Obese Class II | 35.0+ | 30.0+ |
Why Does the Asian Standard Differ?
Research consistently shows that Asian populations carry a higher proportion of body fat at equivalent BMI values compared to Western populations. Specifically, at the same BMI, Asian adults show:
- Higher visceral (abdominal) fat
- Greater risk of Type 2 diabetes and cardiovascular disease
- Earlier onset of metabolic syndrome
This is why countries including South Korea, Japan, China, and Singapore use stricter BMI thresholds.
When BMI Is Not Accurate
BMI has well-known limitations:
- Athletes: High muscle mass raises BMI without excess fat
- Pregnant women: Normal weight gain affects BMI without reflecting health risk
- Older adults (65+): Standard BMI thresholds may not apply
- Children: BMI must be compared to age- and sex-specific growth charts
For a more complete picture, consider also measuring waist circumference and body fat percentage.
How to Use the BMI Calculator
Enter your height and weight (metric or imperial) and the calculator instantly returns your BMI, WHO classification, Asian classification, and your healthy weight range in kg. No account required, no data stored.