Total Length
Based on the side seam of the pants, measure straight down from the very top of the waist to the hem.

Waist
Align the front and back of the waist neatly, then measure horizontally from the left end to the right end.

Hip
Mark a point approximately 20cm below the waistline based on the side seam, then measure horizontally from the left end to the right end.

Thigh
Based on a point approximately 2.5cm below the lowest point where the crotch seams meet, measure from the left end to the right end.

Hem
Based on the cross-section of the very bottom of the pants, measure the horizontal length from one end to the other.