Fabric Calculator

Fabric is sold by length off a roll of fixed width, so the question is never "how many square yards". It is "how many times does my piece fit across the width, and how long does each of those runs need to be".

That is why fabric width matters so much. A 60-inch-wide curtain panel fits in one width of 60-inch home-decor fabric but needs two widths of 44-inch quilting cotton, which doubles the yardage even though the finished curtain is identical.

Every project then adds its own allowances. Curtains need eight inches at the bottom for a doubled hem and four at the top for the header. Pillow covers need a seam allowance plus two overlapping back panels. Quilt backing needs four inches of overage on every side so it can be loaded on a frame. Those allowances are built in rather than left for you to remember.

1. Step 1 Usable width usable = fabric_width − 1 in Half an inch of selvedge each side is unusable.
2. Step 2 How many widths across widths = ceil(piece_width ÷ usable) Curtains, piece_width = window × fullness ÷ panels.
3. Step 3 Cut length per width cut = finished_length + allowances Curtains +12 in, skirts +4 in, quilt backing +8 in, tablecloths +2 in.
4. Step 4 Round up to the pattern repeat cut = ceil(cut ÷ repeat) × repeat Only if the fabric has a repeat. This is where patterned fabric gets expensive.
5. Step 5 Total, in yards yards = widths × cut ÷ 36, rounded up to the next ¼ yard

For example, a pair of curtains for a 48-inch window at 2× fullness needs 48 in of gathered width per panel. On 44-inch fabric that is two widths per panel, four widths total, each cut at 96 in. That is 384 inches, or 10.75 yards.

• One inch is deducted from the stated fabric width for selvedges. Some fabrics have wider unusable edges, particularly printed home-decor cottons.
• Curtain allowances are 8 inches for a doubled bottom hem and 4 inches for a rod-pocket or tape header, plus 2 inches total for side hems. Pinch-pleat or interlined curtains need more.
• Curtain fullness defaults to 2×, which is the standard for a gathered heading. Wave and eyelet headings often specify 2.2–2.5×; flat panels use 1.5×.
• Pillow covers assume an envelope back with two panels overlapping by about 40% of the pillow height, and a 0.5 inch seam allowance. The two back panels are laid side by side wherever the fabric is wide enough to take them, which is the case for most cushions on most fabric, and end to end when it is not. Zipped covers need slightly less fabric but more hardware.
• Quilt backing includes 4 inches of overage on every side, which is what most longarm quilters ask for. If you are quilting it yourself on a domestic machine, 2 inches is usually enough.
• Pattern repeat is applied by rounding every cut length up to a whole repeat. This is what makes patterns match across seams, and on a large repeat it can add 20% or more to the total.
• Nothing here accounts for shrinkage. Cotton and linen lose 3–5% on the first wash, so pre-wash before cutting or buy extra.
• Directional prints and napped fabrics such as velvet must all be cut the same way up, which can prevent efficient nesting of pieces. The estimates here assume a non-directional fabric.