Take and note the measurements before you calculate.calculator, measuring tape and pens isolated on white image by Elnur from Fotolia.com
Measure the width of the area to be covered between the brackets holding the curtain rod. Then measure the height from the floor to the rod or track from which the curtains will hang. Write down both measurements.
The bunching and length of the panels affects the overall appearance.interior - living room image by Kirubeshwaran from Fotolia.com
Decide on the look you are trying to achieve. According to Crate and Barrel, a home furnishing retailer, a smooth, less-layered look will create a more tailored appearance while heavily bunched up curtain panels will have a more dramatic effect. They also suggest leaving a 1-inch clearance from the bottom of the panel to the floor for a clean look, while "puddling" the panels on the floor by leaving 6 to 8 inches of extra length laying on the floor will add to a dramatic look.
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Select a fabric you like. Drapery fabric widths range from 36 to 60 inches wide. Note the width of the fabric you select.
Calculate yardage to save money.girl with money image by Vasiliy Koval from Fotolia.com
Consider the amount of bunch and length you want. Denver Fabrics, on online fabric retailer, says 4 inches should be added to each side hem measurement for a double folded hem, so subtract 4 inches from each side of each panel in your finished width measurement. Then add 10 to 12 inches extra to the length of the panel to allow for a 5 to 6 inch double hem. They also suggest adding 1/2 inch to the diameter measurement of the rod plus about 1 inch to create the rod pocket. After you account for these adjustments, you will have calculated your finished cut length and the width you have to work with once the side hems are sewn. Based on coverage width and the amount of bunch, estimate the number of panels you need. Multiple the number of panels by the finished cut length per panel to calculate the total inches in length. Divide the total inches by 36 to determine the total yards needed.