Background: Common surgical procedures on the mitral valve of the heart include modifications to the chordae tendineae. Such interventions are used when there is extensive leaflet prolapse caused by chordae rupture or elongation. Understanding the role of individual chordae tendineae before operating could be helpful to predict if the mitral valve will be competent at peak systole. Biomechanical modeling and simulation can achieve this goal. Methods: We present a method to semi-automatically build a mitral valve computational model from micro CT (computed tomography) scans: after manually picking chordae fiducial points, the leaflets are segmented and the boundary conditions as well as the loading conditions are automatically defined. Fast Finite Element Method (FEM) simulation is carried out using Simulation Open Framework Architecture (SOFA) to reproduce leaflet closure at peak systole. We develop three metrics to evaluate simulation results: i) point-to-surface error with the ground truth reference extracted from the CT image, ii) coaptation surface area of the leaflets and iii) an indication if the simulated closed leaflets leak. Results: We validate our method on three explanted porcine hearts and show that our model predicts the closed valve surface with point-to-surface error of appoximately 1mm, a reasonable coaptation surface area, and absence of leak at peak systole (maximum closed pressure). We also evaluate the sensitivity of our model to changes in various parameters (tissue elasticity, mesh accuracy, and the transformation matrix used for CT scan registration). We also measure the influence of the chordae tendineae positions on simulation results and show that marginal chordae have a greater influence on the final shape than intermediate chordae. Conclusions: The mitral valve simulation can help the surgeon understand valve behaviour and anticipate the outcome of a procedure.