Getting Started
Things to know before starting:

• Style of treatment (pinch pleat, stack direction, lined or unlined, etc.)
• Area to be covered: rod width and finished length
• Fabric width & repeat
• Quantity
• Hardware: new or existing and hardware type

For example, all calculations will be based on the following specifications:

• Pinch pleat drapery, lined, center opening, 2X fullness
• Rod width 56" x 64" finished length 
• Fabric is 54" wide with an 8" repeat
• New ceiling mount front mount baton draw hardware

Calculations
Number of widths of fabric needed:

Add the rod width and overlap/returns, multiply by fullness and divide by fabric width. The result of this calculation is the number of widths of fabric needed to make the drape:

1. Add Rod width and overlaps/returns (56 + 12 = 68)
2. Multiply by fullness (68 x 2 = 136)
3. Divide by fabric width (136 / 54 = 2.52)

2.52 widths should be rounded up to 3 widths. This means that 3 widths of fabric is required to cover the given window size with the specified fullness. Since it’s a pair (center opening), there will be 1.5 widths of fabric used on each side. (Note: we only work with full and 1/2 widths of fabric. If calculations come out to 1/4 width, round up to 1/2.)         
          
Cut length of fabric:       
For drapery fabric, add to the finished length 15" for hem & heading allowance. If the fabric has a repeat, that must be considered as well. When working with a repeat, the cut length must be divisible by the size of the repeat. If the result of the finished length + 15" is not divisible by the repeat, then round up to the next whole number, and multiply that by the repeat. The result is what the cut length should be. For lining, add 10" to the finished length for hem and heading allowance.

1. Finished length + 15" (68 + 15 = 83)
2. Check cut length w/ repeat size [8"] (83/8 = 10.5)
3. Round result up to next whole number (10.5 round up to 11)
4. Multiply number by repeat (11 x 8 = 88" cut length)

Calculating Yardage
Multiply number of widths per window by cut length in inches. Divide the result by 36" to get number of yards required. Multiply the yards by 5% (working allowance) and add that to number of yards required. Round up to nearest whole number or 1/4 yd.

1. Number of widths x cut length (3 x 88" = 264")
2. Divide by 36" = yards (264" / 36" = 7.33 yards)
3. Multiply yards by 5% (7.33 yards x 5% = .37)
4. Add result to yardage (.37 + 7.33 = 7.70 yards)
5. Round up (7.70 round up to 7.75 yards)