What is BMI
Body Mass Index (BMI) is a simple measure, developed by Belgian statistician Adolphe Quetelet, used to estimate whether a person's weight is appropriate for their height. It's the most common screening tool used by health professionals worldwide.
How to calculate (formula)
BMI = weight (kg) ÷ height² (m). Someone weighing 70 kg at 1.70 m has a BMI of 24.2 — normal weight.
Classification table (WHO)
| BMI | Classification |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Normal weight |
| 25.0–29.9 | Overweight |
| 30.0–34.9 | Obesity class I |
| 35.0–39.9 | Obesity class II |
| 40.0+ | Obesity class III |
Limitations
BMI doesn't distinguish muscle mass from body fat, so it may not accurately reflect athletes, older adults, pregnant women or children. Treat it as an initial screening, not a diagnosis.
Frequently asked questions
What is BMI?
A measure relating weight and height to indicate whether someone is underweight, normal weight, overweight, or obese.
How is BMI calculated?
By dividing weight in kg by height in meters squared.
Is BMI accurate for everyone?
Not entirely — it doesn't distinguish muscle from fat, so athletes and older adults may get a skewed reading.
What range is considered healthy?
Between 18.5 and 24.9, according to the WHO, for most adults.