The measurement of “damage width” from silicone-impregnated specimens reveals the area in which bond failures and other microscopic fractures take place. We demonstrate that damage width is a reasonable measure of the size of the fracture process zone in the sense of fracture mechanics. Firstly, the decay of cohesive stress against crack widening scales with damage width. Secondly, we can calculate the tensile strength of paper from fracture mechanics using damage width as the size of the fracture process zone. Armed with this interpretation, one can use damage width to evaluate, for example, the effective length and strength of fibers in paper.