Curtain Fabric Width Calculator
Buying curtain fabric means turning a window measurement into a number of fabric drops and a yardage. The covered width is multiplied by a fullness ratio to set how gathered the curtain looks, then divided by the usable width of your fabric bolt and rounded up to whole drops, because each drop is cut from a full width. Each drop is cut longer than the finished length to allow for the header and the hem. This calculator does that whole chain and reports widths needed, total cut length, and yardage to buy.
Curtain fabric formula
Total flat width = width to cover * fullness ratio
Widths needed = ceil(total flat width / usable fabric width)
Cut length per drop = finished length + header and hem allowance
Total cut length = widths needed * cut length per drop
Yards to buy = total cut length / 36
Widths are rounded up because each drop must come from a full bolt width. Yards are computed from total cut length divided by 36 inches per yard. Buy a little extra to square the cut and to allow for shrinkage on washable fabric.
Measuring and fullness notes
- The width to cover is usually the curtain rod or track length, not the glass width, so panels overlap the frame.
- Fullness of about 2.0 gives a standard gathered look; sheers and pinch pleats often use 2.5 to 3.0.
- Usable fabric width is the bolt width minus the selvedge you trim; common decor fabric is 54 inches wide.
- One yard equals 36 inches, the United States customary definition used for fabric sold by the yard.
- Patterned fabric needs extra length per drop equal to one pattern repeat so adjacent drops match.
Curtain fabric: frequently asked questions
How much fullness do curtains need?
Fullness is the ratio of total fabric width to the width the curtain covers. A flat panel is 1.0, a gathered look is typically 2.0 to 2.5, and a very full pinch-pleat or sheer look can be 2.5 to 3.0. This calculator multiplies your covered width by the fullness ratio you enter to find total flat fabric width before dividing into bolt-width drops.
How many fabric widths do I need?
Total flat fabric width equals the width you want to cover times the fullness ratio. Divide that by the usable width of your fabric bolt and round up to a whole number, because partial drops must be cut from a full width. This calculator rounds the number of widths up automatically.
What allowances should I add to the cut length?
Each fabric drop must be longer than the finished curtain to allow for the top header and the bottom hem. Add your header allowance and hem allowance to the finished length. A common combined allowance is 8 to 16 inches, but enter the figures your sewing pattern specifies.
How is total yardage calculated?
Multiply the number of widths by the cut length per drop (finished length plus header and hem) to get total linear inches of fabric, then divide by 36 to convert to yards. This calculator reports both total cut length in inches and the yardage rounded for purchase.
Does this account for pattern repeat matching?
No. Patterned fabric that must be matched drop to drop needs extra length per drop equal to one pattern repeat. If your fabric has a repeat, add the repeat length to your header or hem allowance input so each cut length includes the matching allowance.
Official sources
- U.S. National Institute of Standards and Technology: Unit Conversion (yard and inch definitions).
- NIST Handbook 44: Specifications, Tolerances for Weighing and Measuring Devices.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.