How are you supposed to measure the window for curtains?

To measure for curtains, start by determining the width and height of the window. For width, measure from one side of the window frame to the other, then add extra inches for the desired curtain fullness and to allow the curtains to hang outside the frame. For height, measure from the top of the window frame to where you want the curtains to fall, typically just above the sill or to the floor. If you're using a curtain rod, measure from the top of the rod to the desired length as well.