| Category | BMI Range | Description |
|---|---|---|
| Underweight | Below 18.5 | May indicate malnutrition or other health concerns |
| Normal weight | 18.5 – 24.9 | Associated with lowest health risks |
| Overweight | 25.0 – 29.9 | Increased risk of heart disease and diabetes |
| Obese (Class I) | 30.0 – 34.9 | High risk of weight-related conditions |
| Obese (Class II) | 35.0 – 39.9 | Very high risk |
| Obese (Class III) | 40.0 and above | Extremely high risk |
A healthy BMI is between 18.5 and 24.9 according to the World Health Organization. This range is associated with the lowest risk of weight-related health problems. However, BMI is a screening tool, not a diagnostic measure — it does not account for muscle mass, bone density, or fat distribution.
BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = weight (kg) ÷ height (m)². For example, a person weighing 70 kg at 175 cm has a BMI of 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.86. In imperial units: BMI = (weight in lbs × 703) ÷ (height in inches)².
The standard BMI categories are: Underweight (below 18.5), Normal weight (18.5–24.9), Overweight (25–29.9), and Obese (30 and above). Obesity is further divided into Class I (30–34.9), Class II (35–39.9), and Class III (40+). These thresholds may differ slightly for Asian populations.