the measure is simple. the outseam minus the inseam = the rise. on the tailors patterns its where you see true rise on the diagram. its a mistake to measure down the fly and through the curve to the crotch. when ordering on the web, that will give you a baggy rise/crotch area. but it will work when you are comparing two different trousers. ready to wear is always measured from the top of the waistband m2m usually does the same but some times from the bottom of the band. custom tailors usually measure from the top of the hip bone. that is a body measure that represents the bottom of the waist band. some m2m want the body measure.