See tools. There are several online tools for calculating bmi (http://www. Bmi-calculator. Net/body-fat-calculator/, http://www. Livestrong. Com/tools/body-fat-calculator/, http://www. Nhlbisupport. Com/bmi/) then, more accurately, a dietician or other trained profession can do a caliper measurement. There is a bioelectric impedence scale, and recently the usaf uses a "bod pod" to calculate body density and fat.