Window with Rod

• The curtain valance should measure about one and a half to two times the width of the curtain rod on which it is placed. Measure the usable width of the existing curtain rod, not including any hardware on the ends, and multiply this by one and a half to two.
  
  

Window without Rod

• Windows that do not have curtain rods installed yet can still be measured for curtain valances. Measure the inside width of the window frame and add six inches because curtain rods extend three inches on each side of the window. Multiply this total by one and a half to two to find the valance width.
  
  

Bottom Line

• Curtain valances should be one and a half to two times the usable width on the rod on which they are hung. Valances made of thicker fabrics may only need to be one and a half times the width, but sheer valances need two times the width for fullness.