How to Calculate BMI: Formula, Chart & What It Means
BMI is calculated by dividing your weight in kilograms by your height in meters squared. Here's the full formula, a reference chart, and what your number means.
What Is BMI?
Body Mass Index (BMI) is a number calculated from your height and weight used as a screening tool for weight categories.
BMI does not measure body fat directly, but correlates well with direct measures of body fat for most people.
The BMI Formula
Metric: BMI = weight (kg) ÷ height (m)²
Imperial: BMI = (weight (lbs) ÷ height (inches)²) × 703
Example: 70 kg, 1.75 m tall → 70 ÷ 3.0625 = 22.9
BMI Categories
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Normal weight |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obese (Class I) |
| 35.0–39.9 | Obese (Class II) |
| 40.0+ | Severely obese |
Limitations of BMI
- Muscle mass: Athletes often have high BMI without excess fat.
- Age: Older adults may have more fat at a lower BMI.
- Ethnicity: Cut-offs were established from European data.
Use our free BMI calculator to get your exact number instantly.
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