The body mass index (BMI) is a measure of relative weight based on an individual's mass and height. Simply put, it measures the relative 'thickness' of a person, with higher numbers representing a thicker or heavier person, thus allowing health professionals to discuss overweight and underweight problems more objectively with their patients. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat. To measure body fat, you would need to use a Body Fat Calculator.
The Body Mass Index was devised by Belgian Adolphe Quetelet between 1830 and 1850 during the course of developing "social physics", The BMI formula is defined as the individual's body mass divided by the square of their height – with the value universally being given in units of kg/m2, and can also be represented in US pounds/ft2.
BMI can also be determined using a table or from a chart which displays BMI as a function of mass and height using contour lines, or colors for different BMI categories, and may use two different units of measurement; US or Metric.
The BMI is used in a wide variety of contexts as a simple method to assess how much an individual's body weight departs from what is normal or desirable for a person of his or her height. There is however often vigorous debate, particularly regarding at which value of the BMI scale the threshold for overweight and obese should be set, but also about a range of perceived limitations and problems with the BMI.