Friction factor is a crucial parameter for assessing and modelling the ventilation system in underground mining, becoming essential as we deepen the mining activity. This parameter is related to the loss of energy due to air friction inside the mine and consequently to the energy consumption in the fans. So, it must properly calculate in order to reduce operating costs and thus improve mineral prices. This paper presents the calculation of the friction factor through a CFD model of a potash mine case study for different mean roughness and typical velocities. Results are compared with friction factors calculated through traditional empirical relationships. The comparison of both data has given some differences, especially for relative high Reynolds numbers, for low Reynolds numbers it is verified that there is also a dependence with himself. Thus, it is proposed a correction for calculate friction factor with Colebrook-White and Von Karman expressions for the particular case of potash mines.