Quilt Backing Calculator
Calculate fabric requirements, compare panel layouts, and print a plan for cutting and assembly.
How the calculations workEnter measurements Compare layouts View or print your selected plan
2 Compare layouts
Enter your quilt dimensions to get started.
A little measuring.
A plan you can keep.
See your backing size, compare fabric lengths, and choose a cutting plan to print.
Have a 60 × 80 inch quilt in mind?
Try “Load example” to see the working.
For your selected layout
How this purchase is calculated
Both drawings keep the quilt top upwards and use the same scale. Solid outlines show required backing, dashed lines show joins, hatching shows panel trimmings, and arrows beside the fabric show lengthwise grain. Drawings are schematic.
Backing settings used
Directions refer to the quilt as drawn, not to the machine rollers. Longarm loading often favors seams parallel to the rollers; rotating the quilt may conflict with the quilting design. Hanging quilts may need lengthwise grain top to bottom. Confirm these choices and the print direction with your quilter.
The working behind your plan
A simple, straight-panel method
Add twice the per-side extra to each quilt-top dimension. A 60 × 80 inch top with 4 inches on each side needs 68 × 88 inches of backing.
Each panel is a separate length cut from the bolt, using its full usable width. Sew the joining edges right sides together using the selected allowance on each edge, open out the panels, and press the seam allowances open. Press the backing flat and check squareness. Then trim only the right edge (vertical seams) or bottom edge (horizontal seams) to the required backing size, retaining the extra on all four sides until quilting is complete. Allow separately for preparation losses; purchase rounding alone does not guarantee enough for washing or squaring.
For n panels of usable width F, with allowance S per joined edge, assembled width is n × F − 2 × S × (n − 1). One panel has no joined seam and loses no width to seams. We use the smallest panel count that covers the target in each orientation.
Three different allowances
Extra backing enlarges the rectangle around your quilt top. Seam allowance is used inside the fabric where pieces are sewn together; the calculator subtracts it once on each joining edge. Purchase rounding adds length at the shop, after the cuts are totaled. That extra length is separate from the strips trimmed off the assembled backing.
A worked example
With a 60 × 80 inch top, 4 inches extra per side, 42-inch usable fabric, and 0.5-inch seam allowances:
- Vertical seams: cut two 42 × 88 inch panels. The join gives 83 × 88 inches; trim a 15 × 88 inch strip from the right. Use 176 inches of bolt length and buy 5 yards when rounding up to ⅛ yard.
- Horizontal seams: cut three 42 × 68 inch panels and rotate them for assembly. They give 68 × 124 inches; trim a 68 × 36 inch strip from the bottom. Use 204 inches of bolt length and buy 5.75 yards.
Vertical seams use less fabric in this example. The 4 inches of extra purchased with 5 yards are separate from the strip trimmed off the assembly.
Before you cut
Which fabric width should I enter?
Measure the prepared fabric after any washing, drying, and pressing, then exclude both selvages. Keep seam allowances within this usable width: the calculator deducts them at the joins. A bolt's advertised width can include edges you will remove. Wide backing can sometimes cover your quilt with one panel. It still has a lengthwise grain direction, even with no seams.
Is 4 inches extra always enough?
No. The 4-inch extra and 0.5-inch seam defaults are editable examples. Your quilter, frame, or method may require different allowances. The result includes the extra on all four sides already. Zero extra is allowed for arithmetic planning, but is not a general quilting recommendation.
Does this find the least fabric possible?
It compares only two straight-panel orientations, with each panel cut separately. Offcut reuse, nested cuts, and diagonal piecing may use less fabric. They are not included.
What about seam placement?
Panel widths determine seam positions. We do not move a seam away from the center fold or align a pieced backing with the quilt front. Quilting and loading can shift the layers. Check the shown seam locations with your quilter; a different piecing method may be needed.
What about prints and washing?
No extra length is added for pattern matching, directional-print optimization, shrinkage, squaring the bolt ends, or cutting errors. Check these separately before buying. This release assumes stable woven quilting cotton. Stretch or pile fabrics such as Minky, Cuddle, and fleece, sheets, reversible quilts, and precisely centered backing designs need separate planning. This planner is for rectangular quilts; it does not calculate batting or binding or guarantee longarm suitability.
Why might my purchase quantity be the same?
Different raw lengths can round up to the same shop increment. The comparison uses raw length, and each option shows both quantities.
How precise are the measurements?
Enter decimals using a dot, not fractions or commas. Displayed measurements use up to six decimal places; converted values are retained internally until you edit that field. A cutting sheet is unavailable if those decimals cannot express its dimensions accurately in the selected units. The full-precision fabric calculation remains available; try the units used on your ruler. Measurements must be from 0.001 to 10,000 inches (0.00254 to 25,400 cm); extra backing may also be zero. Each orientation is limited to 100 panels.