How to Figure Yardage for a Gathered Valance

Measure the length of the installed curtain rod. If the rod has returns that jut out from the wall, include these two side measurements. For example, for a 48-inch-long continental rod with a clearance of 3 1/2 inches, add 48 plus 3.5 plus 3.5 for a total of 54 inches wide. Record this rod face width in inches.

Multiply the rod face width by a fullness factor for gathers. Examples include a factor of 1.5 for a less gathered look, or 2 for a fuller look. In this example, for a less gathered look, multiply 54 inches by 1.5 to calculate 81 inches for the valance width. A 48-inch rod with returns holds a valance measuring approximately 81 inches wide.

Measure the drop of the valance down to the desired finished lower hem. For example, if your valance contains a 3-inch frill above the rod casing, measure the vertical distance from 3 inches above the top of the rod down to the lower hem. Record this measurement as the finished length. Add the hem allowance for the top and bottom hems to calculate the cutting length. Record the cutting length. For example, if the top hem is 7 inches and the bottom hem is 1 inch, add 8 inches to the finished length to calculate the cutting length of the fabric. This cutting length is always longer than the finished length.

Bring your measurements and a calculator to the fabric or drapery store. Divide the rod face width by the actual width of the fabric. This width usually is labeled on a tag on a roll or bolt. In this example, if the drapery fabric is 54 inches wide, divide 81 inches by 54 inches to calculate a fullness of 1.5. Round this number up to a whole number to figure two lengths of fabric.

Multiply the lengths of fabric by the cutting length in inches. To calculate the yardage, divide this amount by 36 inches. Round up the yardage to a whole number, and purchase extra in case of error or shrinkage.