Question: how to calculate body fat percentage from circumference measurements?
Answer: Younger Women (17-26 years) % Body Fat = (abdominal circumference x 1.34) + (thigh circumference x 2.08) – (forearm circumference x 4.31) – 19.6. ... 
Older Women (over 26 years) ... 
Younger Men (17-26 years) ... 
Older Men (over 26 years)