What is BMI?
BMI is a numerical value calculated from a person's weight and height, used as a screening tool to categorize individuals into weight status categories such as underweight, normal weight, overweight, and obese.
Quick Facts
| Full Name | Body Mass Index |
|---|---|
| Created | 2026-02-01 |
| Specification | Official Specification |
How BMI Works
Body Mass Index is a simple calculation that divides a person's weight in kilograms by the square of their height in meters (kg/m²). Developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI provides a quick assessment of whether an individual's weight falls within a healthy range. The World Health Organization defines BMI categories as: underweight (<18.5), normal (18.5-24.9), overweight (25-29.9), and obese (≥30). While BMI is widely used due to its simplicity, it has limitations as it doesn't distinguish between muscle and fat mass, nor does it account for age, sex, ethnicity, or body composition.
Key Characteristics
- Formula: weight(kg) / height(m)²
- Imperial formula: (weight(lb) / height(in)²) × 703
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5-24.9
- Overweight: BMI 25-29.9
- Obese: BMI ≥ 30
- Does not measure body fat directly
Common Use Cases
- Health screening and assessment
- Population health studies
- Insurance risk evaluation
- Fitness tracking applications
- Medical diagnosis support
Example
70 kg / (1.75 m)² = 22.9 BMI