While the 3D imaging industry growing, the ambiguity in evaluating quality of 3D contents remains as a potential barrier. This paper describes a method to evaluate depth perception quality of stereoscopic 3D contents, by observing the depth image gradient magnitude and quantifying the spatial variations using it. Experimental Results show high correlation between predicted depth perception from our method and the MOS test scores. Also, notable results have been found from depth images with known quality grades that can help enhance the method.