Take the advice above and measure point to point for each input and output at its longest setting. I will describe my experience below for reference.
I used George L's for wiring up a rack giz, FX giz, one amp head, 15 pedals, and runs to a pedal board with a MMGT, wah, and volume. I just bought a 100' roll because I knew I wanted an extremely long rack to board run for stage and a short run for studio work. I left some slack in the rack due to sliding shelves, but after all that I have about 10' left.