Measure the exact width between the inside trim for a snug fit, typically used with tension rods for lightweight sheers.
Add 3 to 6 inches of "overhang" on each side of the frame. This allows curtains to "stack back" when open, maximizing light and making the window appear wider. how to buy curtain rods
Mount the rod 4 to 6 inches above the window frame, or approximately 2/3 of the distance between the window and the ceiling, to draw the eye upward and make the room feel taller. 2. Match Rod Diameter to Fabric Weight Measure the exact width between the inside trim