A numerical method for the calculation of a stationary two-dimensional magnetic field in a permanent magnet electrical machine at no-load is presented. The field approach based on Maxwell's equations is used to formulate the vector potential equation with variable tensor coefficients which holds for any point in the machine cross section perpendicular to the shaft axis. The partial differential equation is transformed into a finite-difference numerical algorithm. The set of nonlinear partial-difference equations is solved by the iterative line successive overrelaxation procedure. The method presented here is an extension of the Colorado method of Erdélyi and his associates for finding two-dimensional magnetic fields in electrical machines with electromagnetic excitation.