Everything You Need to Know About BMI
Body Mass Index (BMI) is a screening tool used worldwide by health professionals to estimate whether a person is at a healthy weight relative to their height. While it does not measure body fat directly, it is a useful indicator of potential health risks associated with being underweight, overweight, or obese.
How is BMI Calculated? (The Formula)
The BMI calculation is based on a simple mathematical formula. Depending on the measurement system you use, the formulas are:
- Metric System: BMI = weight (kg) / [height (m)]²
- Imperial System: BMI = 703 × weight (lbs) / [height (in)]²
Our calculator above performs these calculations instantly, ensuring precision without the need for manual math.
BMI Classification Chart (WHO Standards)
The World Health Organization (WHO) defines the following categories for adults over 20 years old:
| BMI Range (kg/m²) | Classification | Health Risk Level |
|---|---|---|
| Less than 18.5 | Underweight | Moderate (Nutritional deficiency) |
| 18.5 – 24.9 | Normal Weight | Low Risk |
| 25.0 – 29.9 | Overweight | Increased |
| 30.0 and Above | Obesity | High to Very High |
Limitations of BMI
While BMI is a great general indicator, it is not perfect. It does not distinguish between muscle mass and fat mass. For example:
- Athletes: Highly active individuals with high muscle mass may have a high BMI but low body fat.
- Elderly: Older adults may have a "normal" BMI but lose muscle mass and have higher body fat percentages.
- Pregnancy: BMI is not applicable for pregnant women.