Simulation of the heat transfer at the end-windings of an electric machine is often restricted by the quality of the coefficients used in the simulation model. This paper presents a method of obtaining correlations between the convective wall heat transfer coefficient (WHTC) and parameters of the end-region of an electrical machine and its operational conditions. The data have been evaluated by computational fluid dynamics (CFD) and validated by measurements. Dimensionless numbers for the WHTCs have been correlated to the simulated data by the Gauss-Newton method. This characterization provides a way of calculating values for the convective WHTC depending on the rotational speed and the end-shield geometry. Due to the used dimension analysis, the result is applicable on scaled geometries. It is not an exact method for calculating the convective WHTC, but provides a tool with sufficient accuracy for most engineering purposes.