In this study we characterize the fracture toughness of ST37-2 thin metal sheet. The toughness of this material is obtained by using the essential work concept on DENT (Double Edge Notched Test) specimens. These tension tests, show the linearity of the maximal force , the maximal displacement and the final displacement versus the ligament length . These results are confirmed numerically using the Gurson, Tvergaard and Needleman (GTN) micromechanical model. The simulations are carried out using Abaqus software package. A good correlation is obtained between the numerical value of and the essential work of fracture .