It is well-know that the presence of surfactant critically decreases the velocity of bubbles. This is explained by the Marangoni effect, which implies that the shear-free boundary condition imposed in the gas-liquid interface is no longer valid, and this leads to an increase in the drag force on the bubble. Most mathematical models proposed in the past to simulate the increase in the drag as a function of surface contamination assumes the stagnant cap hypothesis. In this work, the steady drag for spherical bubbles moving to its terminal velocity in a liquid contaminated with surfactants was obtained via numerical simulations for 50≤ Re ≤200 by using Comsol Multiphysics® 3.5a with the stagnant cap hypothesis. Different levels of surface contamination from clean bubble up to fully contaminated bubble were considered. The numerical values of drag force, flow velocity and pressure fields as function of the grade of contamination and Re were examined. Additionally, the flow regime (Re) under which a recirculating zone is formed behind a spherical bubble is numerically determined for each extent of the angle of contamination. The agreement of the numerical results with reported drag values was proved. By using an appropriate normalization of the numerical data, a simple explicit drag law for contaminated bubbles as function of the stagnant cap angle was obtained.