There are 3 basic things you need to know to get the "right" fit or to be able to describe your item. Rise - Inseam - and waist.
The "rise" of a jeans is determined by the distance between the crotch up the zipper to the button at the waist. The rise is usually around 12 inches on regular pants. In comparison, the average measurement of low-rise jeans is roughly 8 inches, with some as little as 3-4 inches. They are intended to sit about 3 inches below the belly button.Low rise jeans are also called lowcut jeans, hipsters, hip-huggers and lowriders jeans are very popular today.
To measure "inseam", stand up straight with his legs slightly apart or take a pair of jeans and fold them in half. Using measuring tape, measure from just below the crotch to the bottom of the ankle or to the hem of the pant. Record the length in inches; this is the "inseam".
The easiest way to measure the "waist" on a pair of jeans is hold the pants up flat and stretch the tape measure from one side of the inside waistband to the other side. Don't stretch the pants if they have stretch in them. Then you just double the number- example 12" across = 24" waist.