A dead giveaway that drapes are not custom-made is the lack of pattern matching across the panels of fabric. When in the open position, concentrated pattern colors make this lack of matching even more evident. Matching the pattern starts with calculating the amount of fabric you need, whether you are making the drapes yourself or having someone else do the work. The right amount of fabric to match the pattern is a critical step when making drapes.
Calculate the number of widths of fabric you need for the project. Multiply the finished width of the drape by the required fullness and divide the result by the width of the fabric, then round the number up to the next whole number. For example, for a drape 70 inches wide, at two times fullness and using drapery fabric 54 inches wide, you need three widths of fabric, 54 inches wide. The drapery design determines the fullness of your drape. Typical fullness varies from one and a half for grommet-topped drapes to three times the width for sheers.
Determine the pattern repeat. This is the size of the pattern and all patterns repeat along the length on drapery fabric and across the width on upholstery fabric. For example, a bouquet of roses may measure 26 inches from the tip of the top rose to the tip of the same rose in the next print of the pattern. This fabric has a “26-inch repeat.” Some patterns are very easy to see, such as a vase of flowers. Some are more difficult to determine, such as a plaid or very large abstract pattern, but every pattern repeats in fabric. You will not find any random patterns on machine-printed fabric. For prints without a very visible top of pattern, such as a swoosh of color in an abstract print, choose any identifiable spot on a print and measure to the same spot on the next print for the pattern repeat. If there is information printed on the selvage, measure from one occurrence of a word to the next occurrence of the word to establish the repeat.
Establish the basic required cut length of the drapery fabric. Based on your drapery design, this is equal to the finished length of the drape plus hem allowance and heading allowance. For example, if your drapes must finish at 80 inches long, and you want a 4-inch double hem plus 4 inches for the top fold, your basic cut length is 92 inches.
Divide the basic cut length by the pattern repeat and round the figure up for the number of repeats you require per panel length of fabric. For example, if your cut length is 92 inches, and the repeat is 26 inches, you will need four repeats per cut length panel.
Multiply the number of repeats per panel by the repeat length for the actual cut length per panel. Continuing the example, four repeats of 26 inches equals 104 inches. Each panel you cut must be 104 inches long to allow matching the pattern across the fabric and panels. Remove the excess from the bottom or top after sewing the widths together.
Multiply the actual cut length required by the number of widths of fabric required. Divide the result by 36 for the number of yards of fabric you need for the project in order to match the pattern. For example, if you need three widths, 104 inches long, you must purchase 8 3/4 yards of fabric. This calculation is based on three times 104 equals 312, divided by 36, which equals 8.6. A good rule of thumb is to add two repeats to the final figure to allow for flaws or misprints. Use the extra fabric to make a cushion or two to match your drapes.