Both our canvases and frames are manufactured considering the metric system. The canvas size you see on the website will be the paintable area. I.e., a 40x50 cm canvas will have a 40x50 cm paintable area + canvas borders. The frame size provided measures the outer edges. 40cm = 15.748 inches 50cm = 19.685 inches It is also possible to have a slight error margin when cutting the canvas or frame bars, but the deviation will be marginal since this is done through a machine.