Formula
Pieces in one row are the usable width divided by the piece width, rounded down. Rows are the quantity divided by that, rounded up. Yardage is rows times the piece length, divided by 36, then up to the next 1/8 yard.
per row = floor(fabric width ÷ piece width)
rows = ceil(quantity ÷ per row)
yards = rows × piece length ÷ 36
If the cloth is not directional, the same sum is run with width and length swapped, and the smaller buy is kept. A piece wider than the goods does not fit in that orientation.
Worked examples
Eight 10 × 12 in pieces, 42 in goods, directional. 42 ÷ 10 is 4 across. Two rows of 12 in are 24 in, which is 0.75 yard.
The same pieces, not directional. Turning them puts the 12 in side across the goods: 3 across, so three rows of 10 in are 30 in, which is more cloth. The page keeps 0.75 yard.
A 50 in square on 42 in directional goods. It does not fit. Turn directional off only if the print allows the square to be cut from a wider way of the cloth. On 42 in goods a 50 in square still does not fit either way.
Reference
Eight 10 × 12 inch pieces, directional, rounded up to 1/8 yard.
| Goods | Across | Rows | Buy |
|---|---|---|---|
| 42 in | 4 | 2 | 3/4 yd |
| 44 in | 4 | 2 | 3/4 yd |
| 54 in | 5 | 2 | 3/4 yd |
| 60 in | 6 | 2 | 3/4 yd |
| 108 in | 10 | 1 | 3/8 yd |
Questions
How many yards for eight 10 by 12 inch pieces on 42 inch fabric?
Four pieces fit across 42 inches. Eight pieces are two rows. Two rows of 12 inches is 24 inches, which is 0.75 yard. That is already on an eighth-yard mark, so the buy amount is 0.75 yard.
What if the print has a direction?
Directional fabric is cut in the orientation you typed. If a piece is wider than the goods, it does not fit. When the fabric is not directional, both orientations are tried and the one that uses less cloth is kept.
Which fabric widths are in the menu?
42, 44, 54, 60, and 108 inches. 42 and 44 are quilting cotton after you decide how much selvage to give up. 108 is a wide back. Type another width if the bolt is different.
Sources
- Pieces per row = floor(usable width ÷ piece width). Rows = ceil(quantity ÷ per row). Yards = rows × piece length ÷ 36, up to the next 1/8 yard.
- Widths in the menu: 42, 44, 54, 60, and 108 in. Non-directional cloth is tried both ways; the cheaper layout is kept.