How To Measure and Order Inside Mounting Find Width Measure exact distance from inside of window frame at the top, middle, and bottom (From left to right). Select the Minimum number as the WINDOW width. Find Height Measure exact distance from inside of window frame at the left, middle, and right (From top to down). Select the Maximum number as the WINDOW Height. Order Width = Exact WINDOW inside width Order Height = Exact WINDOW inside height Round numbers WE WILL TAKE 0.4 INCH DEDUCTION FROM ORDER WIDTH TO FIT YOUR WINDOW. A MINIMUM WINDOW DEPTH OF 2 INCHES IS REQUIRED. Outside Mounting 1. If you want the shade totally cover the window frame Order Width = Final SHADE Width = Window outer frame width + Extra 3 to 6 inches Order Height = Final SHADE Height = Window outer frame height + Extra 5 to 10 inches 2. If you want to mount the shade on the surface of the frame Order Width = Final SHADE Width = Window outer frame width Order Height = Final SHADE Height =Window outer frame height THE SIZE YOU ORDERED IS THE FINISHED SHADE SIZE NOT WINDOW SIZE, WE TAKE NO DEDUCTIONS.