Energy release rate, G, of a Mode I crack is estimated numerically by load displacement procedure in the paper. A, through, edge crack is considered in a thin aluminum 2024-T3 alloy plate. The cracked plate is modeled by finite element method. Values of applied load and crack size are suitably selected to simulate LEFM and SSY regimes. Load line displacements are measured from finite element solution. Values of G are compared with J integral values that are obtained from finite element solution using stress and displacement fields near the crack tip.