The process of making your own curtains starts well before you sit down to sew the first stitch. Before you can even buy your fabric, you have to calculate curtain yardage to determine the necessary amounts. It's one of the most important steps.
You may get by with eyeballing it when you're using solid-colored fabric -- as long as you don't mind buying a good bit extra just in case. With patterned fabric, calculating the yardage in advance is crucial for a proper fit and a professionally made look. Fortunately, the process is simple. Here's how to calculate curtain yardage:
Measure your windows and the wall spaces around them to determine the ideal finished length and width of your curtains. The finished dimensions are the sizes of your curtain panels after all the cutting and sewing has been done.
Measure the width of the fabric you want to use for your curtains. Always measure in inches to calculate curtain yardage. You'll convert the inches to yards later. If you're buying fabric off of the bolt, the width may be listed on the fabric tag or on the sticker at the end of the bolt. If you're buying inexpensive remnants or repurposing vintage drapery panels, spread them out and measure the width with a metal measuring tape.
Subtract seam allowances for side seams or hems from the fabric width. Divide the curtain panel width by the adjusted fabric width. Round the result up to the next whole number for the number of fabric widths you need to make each curtain panel. Multiply the total by the number of curtain panels you need if they're all the same size. For most curtain styles, you'll use two panels to make up a pair for each window.
If you need different panel widths to cover different window sizes, calculate the widths needed for each panel -- or for each pair of panels -- separately, and then add the results together.
If you're using patterned fabric, determine the fabric's vertical repeat. The repeat is the size of the pattern or motif. The vertical repeat runs along the length of the fabric. If you're buying from a bolt, the repeats may be noted. If not, spread the fabric flat. Place the end of your measuring tape at any starting point of the fabric's pattern. Measure along the length of the fabric until the pattern starts to repeat itself. The place where it repeats looks just like your starting point.
Add the hem allowances for the tops and bottoms of your curtain panels to your finished curtain the working length. Then, add the working length to the vertical repeat. The result is the cut length.
Multiply the cut length from Step 5 by the final number of fabric widths you calculated in Step 3. Divide the result by 36 and round up to the next whole yard.
If your curtain style has ties, tabs, ruffles or an attached valance, add the amount of extra fabric recommended by the curtain designer or pattern maker to your total from Step 6. The result is the total number of fabric yards you need to make your curtains.
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