In this work, and by using the finite element method (FEM) in two dimensional elasticity, the changes on the stress concentration factor generated by using different elements of approximation (CST, LST, Q4 and Q8) on flat plates are calculated, it is also a factor of study, if the mesh refinement in nearby to the concentrator affecting the value of the stress concentration factor. This analysis is performed by an algorithm developed in Matlab and compared with the results generated by the analytical method and Comsol Multiphysics simulations