Yard & Bobbin

Quilt Backing Calculator

Estimate how much backing to buy and compare lengthwise and crosswise layouts. Start with the actual size of your finished quilt top.

Your quilt and fabric

The form starts with a 60″ × 72″ throw quilt as an example. Enter measurements in decimal inches, such as 62.125 for 62 1/8″.

Need to measure your quilt top? See our quilt size guide.

Usable width: measure across the prepared fabric after excluding the selvages. The 42″ and 106″ values are examples; check your own fabric.

Edge allowance: 4″ per edge adds 8″ to both dimensions. Ask your longarm quilter how much extra backing they require.

How the estimate works

  1. Add twice the edge allowance to each quilt-top dimension.
  2. Try both orientations. For each, use the fewest full-width panels that cover the required span after joining. A 1/2″ allowance on both edges of a join uses 1″ of the combined width.
  3. Multiply the number of panels by the cut length, divide by 36 inches per yard, then round up to the selected store increment.

Example: A 60″ × 72″ top with 4″ extra on each edge needs a 68″ × 80″ backing. With 42″ usable fabric and a 1/2″ seam allowance, two panels give 83″ across the joins. Cut two 80″ lengths (160″ total, or 4 1/2 yd at 1/8-yard increments), or turn the layout and cut two 68″ lengths (136″ total, or 3 7/8 yd).

This calculator compares rectangular, full-width panels. Scrappy backs, offcut layouts, extra trimming length, and pattern repeats require a separate cutting plan. Quilters may prefer a different seam orientation for loading the backing.

Further reading: APQS on piecing quilt backs, APQS on extra backing, and the Fat Quarter Shop backing reference chart.