Blinds fit either inside or outside the window frame, depending on the type you choose. An inside fit is less intrusive on the sense of space in the room and offers better insulation.

To measure for an inside fit make sure your window frame is square by taking two measurements. Take one measurement along the top of the frame and one along the bottom, this is the width. The smaller of those two measurements should be used to ensure the blind isn’t too big when it arrives for installation. It is imperative to take your measurements to the nearest millimeter. To measure the ‘drop’ take two measurements again, one from the top to the bottom on both the left and right side of the window frame. Once again the smaller of the two measurements will be used.

For an outside blind, take your two measurements again for the width, from the outside of the architrave to the other side of the opposite side architrave. The least of the two numbers will be utilized. For the drop, measure from the top of the architrave bearing in mind you may want the blinds to fall below the window framing. So just measure it down to where you want the blinds to hang to. Keep in mind any obstructions around the window frame that may get in the way.