Health
The BMI Formula & WHO Weight Charts: Health Metrics for Men and Women
Just ask and get Editorial Team(Health & Clinical Metrics)
Updated 2026-09-20
7 min read
Key Takeaway:A complete overview of Body Mass Index calculation formulas, clinical health categories, and athletic interpretation caveats.
The Body Mass Index Equations
BMI can be computed using either metric or imperial units:
- **Metric Formula:**
$$\text{BMI} = \frac{\text{Weight (kg)}}{[\text{Height (m)}]^2}$$
- **Imperial Formula:**
$$\text{BMI} = \frac{\text{Weight (lbs)} \times 703}{[\text{Height (inches)}]^2}$$
World Health Organization (WHO) Adult Classifications
- **Underweight:** BMI < 18.5
- **Healthy / Normal Weight:** BMI 18.5 – 24.9
- **Overweight:** BMI 25.0 – 29.9
- **Obese Class I:** BMI 30.0 – 34.9
- **Obese Class II:** BMI 35.0 – 39.9
- **Obese Class III:** BMI ≥ 40.0
Frequently Asked Questions
Why does BMI overestimate body fat in athletes?
Because bone and dense muscle tissue weigh more per unit of volume than adipose fat tissue, athletic individuals can have a high BMI while maintaining healthy, single-digit body fat.