To the nearest eighth of an inch. Start off by measuring the length of the window from the top to the bottom being sure to stay within the mounting. After you’ve established the height of your window then measure its width of the window from left to the right.
There are numerous mounting options in the case of blinds or shades. The mounts are able to be installed to either the outside or the inside of the frame. Take note of the distance between the window and yourself make sure that the blinds are appropriate in depth.