This is how we measure our dungarees here at the ranch.  All measurements are taken flat unless noted:

The waist is measured straight across from side to side and doubled.  Example: 16" flat is a 32" waist or a size 32 dungaree

The front rise is measured from the crotch seam straight up to the top of the waistband.

Similarly, the back rise is measured from the crotch seam straight up the back of the dungarees to the top of the waistband.  In general, the back rise is 3" or greater than the front rise measurement.

The thigh measurement is taken straight across starting from the crotch seam.

The knee measurement is taken from side to side roughly 13" below the thigh.

The hem or leg opening is taken from side to side.

The inseam is taken from the crotch along the contour of the leg to the hem opening.  All WH Ranch Dungarees come in a standard 37" inseam, though custom inseams are available upon request.