How do you calculate body fat percentage?

Body Fat Percentage (BFP) formula for adult males

BFP = 1.20 × BMI + 0.23 × Age - 16.2

Body Fat Percentage (BFP) formula for adult females

BFP = 1.20 × BMI + 0.23 × Age - 5.4

Body fat Percentage (BFP) formula for boys

BFP = 1.51 × BMI - 0.70 × Age - 2.2

Body Fat Percentage (BFP) formula for girls:

BFP = 1.51 × BMI - 0.70 × Age + 1.4