What this estimate does and does not do
This calculator estimates fabric quantity for simple curtains or drapery panels. It does not replace a professional workroom specification. Heading type, lining, interlining, pleats, fabric direction, railroaded fabric, shrinkage, pattern placement, seams, returns, stackback, and workroom methods can change yardage. For expensive patterned fabric, confirm the estimate before cutting.
Formula used
required cut width = rod width × fullness factor + side allowances
fabric widths needed = ceil(required cut width / fabric width)
cut length = finished drop + top allowance + bottom allowance
adjusted cut length = cut length rounded up to pattern repeat, if any
face fabric = fabric widths needed × adjusted cut length ÷ unit divisor × waste factorIn imperial mode, the unit divisor is 36 inches per yard. In metric mode, it is 100 cm per metre.
Worked example
For a 72 inch rod, 84 inch finished drop, 2× fullness, 54 inch fabric width, 4 inch top allowance, 8 inch bottom allowance, and 5% waste:
required cut width = 72 × 2 + 4 = 148 in
fabric widths = ceil(148 / 54) = 3 widths
cut length = 84 + 4 + 8 = 96 in
face fabric = 3 × 96 / 36 × 1.05 = 8.4 ydAssumptions
- The calculator uses the rod or track width, not just glass width.
- Fabric widths are rounded up because you cut whole drops from the bolt.
- Pattern-repeat matching is simplified by rounding each drop to the next repeat.
- Lining is estimated as a separate fabric quantity and may be cut slightly shorter.
Frequently asked questions
How do you calculate curtain fabric yardage?
Multiply rod or track width by the fullness factor, add side allowances, divide by fabric width and round up to full fabric widths, then multiply by cut length.
What curtain fullness factor should I use?
Flat or simple panels may use around 1.5× fullness. Many gathered, pencil pleat, or standard drapery styles use around 2× to 2.5×. Luxury or sheer curtains can use more.
How does pattern repeat affect fabric quantity?
Pattern repeat can increase the cut length because each drop may need to be aligned to the pattern. This calculator rounds each cut length up to the next full repeat.
Should I measure the window or the curtain rod?
Use the rod or track width, including any overhang beyond the window frame, because that is the finished width the curtains need to cover.