[Austin W Hogan]

Chuck is correct; if you use the combo gauge it will give you an angle from rib the butt face that can be compared. If you use the wall method the number is dependant on barrel length, length of pull and drop. It is possible to trigonometrically calculate the pitch angle from this if you know the length from muzzle to heel. It is a lot quicker and easier to use the combo gauge.
Best, Austin