A fluid dynamics software package (Fluent) was used to calculate the local velocities in a standard tank fitted with a Rushton turbine. We defined the local average shear rate (<(gamma)over bar>)over dot as a user variable. The power was computed from the values of (<(gamma)over bar>)over dot with a user subroutine. The influence of the rheological behaviour of the fluid was investigated: the shape factor K-p for a Newtonian fluid, and in the case of a shear-thinning fluid Metzner and Otto＇s concept was used to determine the effective shear rate (gamma)over dot (e).(gamma)over dot verified the classical relation: (gamma)over dot (e) = K-s.N. The influence of position and stirring speed on the local average shear rate (<(gamma)over bar>)over dot was also studied. As expected, higher values were obtained near the turbine. At a fixed position, (<(gamma)over bar>)over dot was found to be proportional to the stirring speed N, The power values obtained by numerical procedures were compared to experimental results: the Fluent software yielded results in excellent agreement with experimental findings. The calculation of local parameters such as the local average shear rate (<(gamma)over bar>)over dot as well as global characteristic shape factors demonstrate the validity of Fluent software in the laminar range.