BMI

BMI, or body mass index, is a simple and widely used method for estimating body fat. BMI was developed by the Belgian statistician and anthropometrist Adolphe Quetelet.

Metric: BMI = kg / m²

Where kg is the subject's weight in kilograms and m is the subject's height in metres.

US/Customary: BMI = lb * 703 / in²

Where lb is the subject's weight in pounds and in is the subject's height in inches.

BMI less than 18.5 is underweight

BMI of 18.5–24.9 is normal weight

BMI of 25.0–29.9 is overweight

BMI of 30.0–39.9 is obese

BMI of 40.0 or higher is severely (or morbidly) obese

BMI of 35.0 or higher in the presence of at least one other significant comorbidity is also classified by some bodies as morbid obesity

BMI overestimates body fat in persons who are very muscular, and it can underestimate body fat in persons who have lost body mass (e.g. many elderly).