Quantification and minimisation of energy consumption in resonant MEMS micromirrors is a key aspect for a proper structural design. In this setting, the quality factor Q of the drive mode of the device needs to be estimated and, eventually, improved. In this work, we propose a simulation strategy for the numerical computation of MEMS micromirrors quality factors. Full order Arbitrary Lagrangian Eulerian Navier-Stokes simulations have been performed using a SUPG stabilised Chorin-Themam scheme. Finally, the numerical results are compared with experimental data, highlighting the accuracy and efficiency of the proposed method.