Body Mass Index (BMI) and Body Surface Area (BSA)

Introduction
Adolphe Quetelet (1796-1874) was a belgian astronomer, mathematician, statistician, and sociologist who founded and directed the Brussels Observatory and was influential in introducing statistical methods to the social sciences. He originally created the equation for body mass in 1832 as a method to define the standard proportions of the human build. Ancel Keys, a physiology professor, used Quetelet's equation as part of a 1972 published report on obesity and created the name body mass index or BMI.

BMI may be a simple and cost-effective measure of body fat. BMI evaluates the relationship of body mass to height, but it may not be accurate for everyone. BMI does not differentiate between the ratio of body fat to muscle present in body mass nor factor gender, developmental or ethnic considerations. Examples of BMI Limitations:

• May be an inappropriate measure for muscular or fit body types. Body fat measurements may be more accurate.

• Ethnic variations in height and stature.
  

BMI offers a more accurate understanding of body composition than weight alone. Additionally, BSA is used in specific therapeutic use cases, such as the treatment of burns.

Rules

• Body mass index (kg/m²) = weight(kg) / (height(m))²

• Body surface area (m²) = (Height (cm) x Weight (kg)  / 3600)^0.5

• Uses the Mosteller formula

Gadzik J. "How much should I weigh?"--Quetelet's equation, upper weight limits, and BMI prime. Conn Med. 2006 Feb;70(2):81-8.