Use a steel tape to measure the opening at three different places, and use the narrowest dimension when ordering. Be exact! The factory will make the shade 3⁄16” narrower so it will not rub against the window casing. Measure the height of the window from the top (soffit) down to the sill.
Use a steel tape to measure the exact height and width of the area to be covered. It is recommended that the shades overlap the window by at least 1” on each side. When installation has no sill, allow the shade to overlap the bottom of the window casing by at least 1”. Shade fabric will measure width indicated on the order form.