Window dimensions
Measure from where your curtain rod will hang down to the floor, or to your desired curtain length.
Fullness
2x fullness is the most common — curtains look gathered but not excessive. Most ready-made panels are designed for 2x.
Panel width
54 inches is the most common ready-made curtain panel width at most home stores.
Number of windows
Frequently Asked Questions About Calculating Curtain Fabric Yardage
Q1. How much fabric yardage do I need to sew curtain panels?
Multiply your desired finished panel width by your fullness ratio (usually 2 to 2.5x) to get the total fabric width needed, then divide by your fabric's width (typically 54 inches) to determine how many fabric widths you'll need to sew together. Multiply that by your finished length plus extra for hems (add about 8-10 inches total for top and bottom hems) to calculate total yardage per panel.
Q2. How does fabric width affect the yardage I need to buy?
Standard decorator fabric is usually 54 inches wide, while quilting cotton is often only 42-44 inches wide. Narrower fabric means you'll need to piece together more widths to reach your desired fullness, which increases your total yardage requirement and adds visible seams unless you plan seam placement carefully (like centering a seam behind a curtain pleat).
Q3. How do fabric pattern repeats affect how much yardage I need?
If your fabric has a printed pattern with a repeat (a motif that repeats vertically at a fixed interval), you need extra yardage so each panel starts and ends at a matching point in the pattern, and so multiple panels line up visually. As a rule of thumb, add one full pattern repeat length per panel to your yardage calculation; large-scale patterns with big repeats (12+ inches) require noticeably more fabric than small prints or solids.
Q4. Should I include hem and header allowances in my yardage calculation?
Yes. Budget roughly 8 inches for a bottom double-fold hem and 6-8 inches for the top header/rod pocket, depending on your curtain style, meaning around 14-16 inches of extra fabric length per panel beyond the finished length. Skipping this allowance is one of the most common reasons DIY curtain-makers run short on fabric.
Q5. How much extra yardage should I buy as a safety margin?
Beyond your calculated total, add an extra half yard per panel to cover cutting errors, shrinkage from pre-washing, and any pattern-matching adjustments. If you're buying a printed fabric with a large repeat, consider rounding up to the next full yard, since most fabric stores sell in whole or half-yard increments and running short mid-project often means the dye lot won't match if you have to reorder.