Understanding Body Mass Index (BMI)
Body Mass Index (BMI) is a simple screening tool that relates weight to height. Healthcare providers use this BMI calculator to quickly assess whether patients fall into underweight, normal weight, overweight, or obesity categories.
How BMI is Calculated
The standard BMI formula uses metric measurements:
BMI = weight (kg) / [height (m) × height (m)]
For those using imperial measurements, the formula adjusts to:
BMI = 703 × weight (lb) / [height (in) × height (in)]
BMI Categories
For adults 20 years and older, BMI categories are:
- Underweight: BMI less than 18.5
- Normal weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25 and 29.9
- Obesity: BMI of 30 or greater
Example Calculations
Metric example: A person weighing 70 kg with height of 1.75 m would calculate: 70 ÷ (1.75 × 1.75) = 22.86 (Normal weight).
Imperial example: A person weighing 154 lb with height of 5'9" (69 inches) would calculate: (703 × 154) ÷ (69 × 69) = 22.75 (Normal weight).
Limitations of BMI
While useful for population screening, BMI has limitations. It doesn't distinguish between muscle and fat, so athletes with high muscle mass may register as overweight. Similarly, older adults with reduced muscle mass might have normal BMI despite higher body fat percentage.
For a comprehensive health assessment, consider additional measures like waist circumference, body composition analysis, and consultation with healthcare providers.