What is BMI? Understanding Your Body Mass Index
Learn what BMI means, how to calculate it, what's a healthy range, and why BMI has limitations for athletes and certain body types.
What is BMI?
Body Mass Index (BMI) is a simple number calculated from your height and weight. It's used as a screening tool to indicate whether you're underweight, normal weight, overweight, or obese.
The Formula
BMI = weight (kg) ÷ height (m)²
Or in imperial: BMI = weight (lb) × 703 ÷ height (in)²
BMI Categories
- Below 18.5 — Underweight
- 18.5 – 24.9 — Normal (healthy weight)
- 25.0 – 29.9 — Overweight
- 30.0 and above — Obese
Limitations of BMI
BMI doesn't distinguish between muscle and fat. A muscular athlete might have a "overweight" BMI while being perfectly healthy. It's best used as one indicator alongside other measures like waist circumference, body fat percentage, and overall fitness level.
When to Use BMI
BMI is most useful as a quick screening tool for the general population. For a more complete health picture, combine it with other measurements and consult a healthcare professional.