The body mass index (BMI), or Quetelet index, is a controversial statistical measurement which compares a person's weight and height. Though it does not actually measure the percentage of body fat, it may be a useful tool to estimate a healthy body weight based on how tall a person is. Due to its ease of measurement and calculation, it is the most widely used diagnostic tool to identify weight problem within a population including: underweight, overweight and obesity. It was invented between 1830 and 1850 by the Belgian polymath Adolphe Quetelet during the course of developing "social physics". Body mass index is defined as the individual's body weight divided by the square of his or her height. The formulae universally used in medicine produce a unit of measure of kg/m2. BMI can also be determined using a BMI chart, which displays BMI as a function of weight (horizontal axis) and height (vertical axis) using contour lines for different values of BMI or colours for different BMI categories.

For more information about Body mass index, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.