Methods and apparatuses for per display scale factors within a multiple display system are described.In one aspect of the invention, a machine implemented method includes setting a scale factor for each window buffer equal to an extreme scale factor among a plurality of displays. The method further includes transferring data from each window buffer into a corresponding frame buffer for one of the plurality of displays by setting a scale factor of each frame buffer equal to the scale factor of the corresponding display.In one example according to this aspect, the method further includes displaying on a high resolution display and a low resolution display an image, stored in the corresponding frame buffers, with substantially the same physical size even though the displays have different scale factors and pixel densities. Also, the extreme scale factor is one of the largest scale factor or the smallest scale factor.