I don't know the math, but I installed some cheap bump stops from Wheeler's Off Road and they work to keep my tire from hitting the top of the wheel well. The rubber part is about 3x the amount of the stock ones, but only 2x taller. They are softer than the stock ones too.
Don't know of an exact way to measure it. Probably have to do some trial and error and video it like the guy in the 4R above or figure out a way to cycle the suspension without flipping over your truck (jack up lower control arm while holding frame level to the ground).