Body mass index

Body mass index (abbreviated BMI) is a rough measure of proportionality between a person's height and weight, and is used to estimate whether a person is at a healthy weight for their height. BMI is calculated as weight in kilograms divided by height in meters squared. For english units, a conversion factor is applied.

${\textrm {BMI}}={\frac {\textrm {W(kg)}}{{\textrm {H(m)}}^{2}}}=4.88{\frac {\textrm {W(lbs)}}{{\textrm {H(ft.)}}^{2}}}=703{\frac {\textrm {W(lbs.)}}{{\textrm {H(in.)}}^{2}}}$.

Healthy BMI is between 18.5 and 24.9. Less than 18.5 is considered underweight; between 25 and 29.9 is considered overweight, over 30 is considered obese, and over 40 is considered morbidly obese.

BMI is a rough diagnostic tool for estimating body fat, and has limitations. Chief among these are that it may overestimate body fat in athletes and others who have a muscular build, and that it may underestimate body fat in older persons and others who have lost muscle mass.