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'''Body Mass Index (BMI)'''

The '''Body Mass Index''' ('''BMI'''), pronounced /ˈbɒdi mæs ˈɪndɛks/, is a value derived from the mass (weight) and height of an individual. The BMI is defined as the individual's body mass divided by the square of their height. It is an internationally used measure of obesity.

==Etymology==
The term "Body Mass Index" was first coined by the Belgian polymath Adolphe Quetelet during the 19th century. It was developed as part of his "social physics" and is sometimes referred to as the '''[[Quetelet Index]]'''.

==Calculation==
The BMI is universally expressed in kg/m², resulting from mass in kilograms and height in meters. If pounds and inches are used, a conversion factor of 703 (kg/m²)/(lb/in²) must be applied. The formula is:

:'''BMI = mass(kg) / height(m)²'''

==Categories==
The World Health Organization (WHO) defines these categories of BMI for adults:

* Underweight: BMI less than 18.5
* Normal weight: BMI 18.5–24.9
* Overweight: BMI 25–29.9
* Obesity: BMI 30 or greater

==Limitations==
While the BMI can contribute to an assessment of an individual's weight and health status, it is to be noted that it is not a direct measure of body fat. Factors such as muscle mass and distribution of fat can influence the BMI.

==Related Terms==
* [[Obesity]]
* [[Overweight]]
* [[Underweight]]
* [[Quetelet Index]]

==See Also==
* [[Body Fat Percentage]]
* [[Waist-Hip Ratio]]
* [[Basal Metabolic Rate]]

[[Category:Medical Terms]]
[[Category:Health]]
[[Category:Physical Fitness]]
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