A method for calculating a process center for a chuck in a processing chamber is provided. The method includes generating pre-processing and post-processing measurement data points, which is perform by measuring thickness of a film substrate at a set of orientations and a set of distances from a geometric center of the substrate. The method also includes comparing the pre-processing and post-processing measurement data points to calculate a set of etch depth numbers. The method further includes generating etch profiles for the set of orientations. The method yet also includes extrapolating a set of radiuses, which is associated with a first etch depth, from the etch profiles. The method yet further includes generating an off-centered plot, which is a graphical representation of the set of radiuses versus the set of orientations. The method more over includes calculating the process center by applying a curve-fitting equation to the off-centered plot.