I have used the Hodgdon and Friedl derived equations for estimating the percent body fat for adults, which were actually developed for the U.S. Department of Defense (DoD). They are the same as the U.S. Navy equations, except the measurements are in inches rather than centimetres.
 

Parameters

(1) gender
(2) height in inches with subject standing tall.
(3) abdomen circumference at the level of the umbilicus in inches (abdomen II)
(4) abdomen circumference at the narrowest point between the lower sternum and umbilicus in inches (abdomen I)
(5) hip circumference in inches at the level of greatest protrusion of the buttocks
(6) neck circumference in inches below the larynx (Adam's apple)
 

Measurement instructions

(1) The tape measure should be nonelastic without stretch.
(2) Height is recorded to the nearest half inch.
(3) Measurements of the abdomen, hips and waist are rounded down to the nearest half inch.
(4) Measurements of the neck are rounded up to the nearest half inch.
(5) The person's arms are to be hanging naturally at the sides.
 

Formulae

(1) male percent body fat = (86.010 * LOG10((abdomen II) - (neck circumference))) - (70.041 * LOG10(height)) + 36.76
 
(2) female percent body fat = (163.205 * LOG10((abdomen I) + (hip circumference) - (neck circumference))) - (97.684 * LOG10(height)) - 78.387