QUILT PLANNING / BACKING
Vertical vs horizontal backing seams
Vertical seams join panels side by side across the quilt. Horizontal seams stack panels from top to bottom. Either can save fabric depending on the dimensions.
Compare the same quilt in both directions
For a 60 × 80 in top, add 4 in on each side to get a 68 × 88 in back. Use 42 in fabric and a ½ in seam allowance on each joined edge.
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| Layout | Cuts | Sewn coverage | Buy |
|---|---|---|---|
| Vertical | 2 × 88 in | 83 × 88 in | 5 yd |
| Horizontal | 3 × 68 in | 68 × 124 in | 5¾ yd |
Count both edges of each seam
Two panels do not provide 84 in of sewn width. The join takes ½ in from each edge, leaving 83 in. A required width just over 83 in forces a third panel in that direction.
Coverage = panels × usable width − 2 × seam allowance × (panels − 1)
When to override Auto
Select vertical or horizontal seams if rotating a one-way print would put it sideways. Ask your longarm quilter about preferred seam placement and preparation. The tool compares yardage, not how a seam will load on a particular frame.
Why there may be another lower-waste layout
These estimates use full-width panels. Splitting offcuts, centering a narrow feature panel or using a diagonal backing technique changes the cutting plan. Auto chooses the lower purchase only among the two layouts shown. It does not claim a global minimum across every possible arrangement.
Try your own sizes in the calculator, inspect the panel diagram, and check whether wide-back avoids the joins.
Read our calculation methods and limits. Examples use the same arithmetic as the calculators and are planning estimates, not independently field-tested sewing instructions. Confirm allowances with your quilter.