Inside Mount:
Measure the exact width of window at 3 different places. Use the narrowest. Measure the exact length from the top window opening to bottom sill. Use the shortest. Measure the depth of window frame, A minimum of 2 1/4" is required. Allowances for clearance are made at the factory.

Outside Mount:
Measure the exact width and length, including all the frame to be covered by blind or shade. If their is a sill, or if blind will go to floor (i.e. patio door), add 3" to length for mounting blind 3" above frame. If their is no sill, add 3" below for light and privacy control. If measuring for sliding door, allow 1 " clearance. To cover all window or frame, the vertical should overlap by 6" in width (3" on either side). Vertical blind will be made to your exact Width and length measurements.