Body fat can be estimated from body mass index (BMI), a person's mass in kilograms divided by the square of the height in meters; if weight is measured in pounds and height in inches, the result can be converted to BMI by multiplying by 703.
Child body fat % = (1.51 × BMI) − (0.70 × Age) − (3.6 × sex) + 1.4
Adult body fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4
where sex is 1 for males and 0 for females.
Description	Women	Men
Essential fat	10–13%	2–5%
Athletes	14–20%	6–13%
Fitness  	21–24%	14-17%
Average	        25–31%	18-24%
Obese	 32% and higher	25% and higher