Measure around your natural waistline, keeping the tape bit loose.
Measure around the fullest part of your body at the top of your leg.
Wrap the measuring tape around the thigh, where the bottom of your butt meets the top of your thighs.
Measure from your belly button going under your crotch, up around the curve of your butt and back up to the waist at your back.
Side length :
Measure along the side, the distance from waistline to ankle.
Wearing pants that fit well, measure from the crotch seam to the bottom of the leg.
Front rise :
Measure from the crotch seam straight up to the top of the waistband
Back rise :
Measure from the crotch seam straight up the back of the dungarees to the top of the waistband