Typically larger than a window’s top frame, a skirt can cover rods, brackets, and other hardware.
The first step in determining the size of the valance is to carefully measure the window that will be treated with a valance. The skirt size will always need to be at least a little wider than the window. Depending on where the hardware is located, the skirt may also need to be wider than the window frame. A skirt is often used to hide rods, brackets, or other hardware, so you’ll want one big enough to cover them and leave plenty of space between the piece and the hardware. For pickups, you’ll need to add a lot more width when setting your skirt size.
Once the curtain rods are in place, you can measure the width of the rod and also the return. Return is the length of space between the wall and the face of the curtain rod. You will need to measure one side and then multiply it by two and add it to the width of the stem face to determine the appropriate skirt size.
For a valance made of wood or made of another solid material, you will need to ensure that its return extends far enough to leave enough space between it and the curtain hardware. For a fabric skirt, you will need enough material to cover the full width, including the return measurements, and leave room for a seam. If you prefer a gathered look, more fabric will be needed. You will need to at least double the size of the skirt and maybe add 50% more depending on how much collection you want.
Once the width has been calculated, it’s time to move on to the length. The length of the skirt is determined by several different elements, including its height and the height of other items in the space. If you want to wear a standard size, a typical skirt is about 14 inches (or 36 centimeters) long from the bottom edge of the stem to the bottom of the hem.
If you plan on doing your own treatment, you need to start calculating your skirt size at least 14” (or 36 centimeters) by adding about an inch (or 2.54 centimeters) to the hem. You will also need to add the proper amount of fabric to the shank pocket. Measure the shank and leave enough additional space to allow it to slide smoothly and include the seams. Add this number to your total. If you want to add a ruffle on top, you will need to add twice the desired ruffle height. A one-inch (or 2.54 centimeters) ruffle requires two inches (or 5.08 centimeters) of fabric.