Abstract : Wide range algebraic expressions for the displacement of cracked fracture mechanics specimens are developed. For each specimen two equations are given: one for the displacement as a function of crack length and the other for crack length as a function of displacement. All of the specimens that appear in ASTM Standard E-399 are represented in addition to the crack mouth displacement for a pure bending specimen. For the compact tension sample and the disk-shaped compact tension sample, the displacement at the crack mouth and at the load line are both considered. Only the crack mouth displacements for the arc-shaped tension samples are presented. The agreement between the displacements or crack lengths predicted by the various equations and the corresponding numerical data from which they were developed are nominally about three percent or better. These expressions should be useful in all types of fracture testing including J sub I sub c, K sub R and fatigue crack growth.