Craft & baking

Quilt backing calculator

Compare backing layouts and turn your quilt measurements into fabric yardage.

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01 / Your quilt & fabric

in
in
in

Use the amount your quilting method or service requires.

in

After removing selvages, before joining panels.

in

Each seam joins two edges and consumes twice this amount.

Round the total up to your shop’s cutting increment.

Changing units converts your measurements. This plan uses equal-length rectangular panels and does not include shrinkage, print matching, squaring or reuse of offcuts.

02 / Your results

5 ydBuy for the shorter layout4.572 m equivalent

Before shop rounding: 176 in of fabric (≈ 4.889 yd).

Compare backing layouts. Fabric requirements are shown in yards before shop rounding, followed by the purchase amount.
LayoutPanels × lengthFabric
Vertical2 × 88 in≈ 4.889 yd
Buy 5 yd
Horizontal3 × 68 in≈ 5.667 yd
Buy 5.75 yd

Cut 2 panels, each 42 in wide × 88 in long. Join with 1 seam.

Target backing: 68 in × 88 in. Vertical seams run along the quilt’s length; horizontal seams run along its width.

The shorter layout may not suit directional prints or your quilter’s preferred seam placement.

How the calculation works

Add the extra backing to both sides of each quilt dimension. For n panels of usable width F with seam allowance s on each joined edge, assembled width is nF − 2s(n − 1). Compare both orientations, then round fabric length up to your chosen purchase increment.

Try an example

A 60 × 80 inch quilt with 4 inches extra per side needs a 68 × 88 inch backing. With 42-inch usable fabric and ½-inch seam allowances, two 88-inch panels use about 4.89 yards, rounded up to 5 yards at ⅛-yard increments.

How to use this calculator

  1. Choose inches or centimetres. Enter the quilt width and height, then the extra backing required on each side by your quilting plan or longarm quilter.
  2. Enter usable fabric width after removing selvages, the seam allowance on each joined edge, and the purchase increment offered by your fabric shop.
  3. Select Calculate backing. Compare the two panel orientations and their cut lengths, then use the rounded purchase amount for the layout that suits your fabric and quilting plan.

Common questions

Is extra backing added to every side?

Yes. Entering 4 inches adds 8 inches to both quilt dimensions. A 60 × 80 inch quilt needs 68 × 88 inches before considering piecing seams. Confirm the required extra with your quilter; the example is not a universal longarm requirement.

How do fabric width and seams affect the result?

Use the width available after selvages are removed. Each seam consumes an allowance from both joined edges, so two 42-inch panels joined with a ½-inch allowance make an 83-inch-wide backing.

Should I always choose the layout using less fabric?

Check grain, directional prints and your quilter's seam preference first. This estimate uses full-width panels and does not add fabric for shrinkage, print matching or extra squaring. Purchase rounding does not guarantee enough for those additions.

Further reading: APQS: how to piece quilt backs