Ask most decorators and they will tell you to always have your window valance (the shirred/gathered style) to be 2 ½ times fullness. This means if your rod is 40” wide, you would want a 100” wide valance (ie: 40 x 2.5 = 100).
While we agree with this most of the time, there are some gathered window valances that look better when they are not so full. For one, balloon style valances when using too much fabric will not look as they should, they will look crowded and droopy.
We also feel that thicker linen type fabrics do not necessarily need to be at industry standards to achieve a custom full appearance. What is most important to some people is not as important to others.
While fullness is often associated with custom draperies and valances, some customers prefer to see more of the actual fabric print, which if the fabric is quite full they will lose.
We list on our website what fullness we suggest for all our gathered styled valances. When in doubt, feel free to send us a quick email or phone call to help you determine the best size to order.