A LITTLE MATH. MORE MAKING.

Quilt backing calculator

Compare backing panel layouts, include seam allowances, and take a cutting list to the fabric shop.

Your quilt & fabric

Measurement unit

Use finished quilt-top dimensions. Unit switching converts your measurements; the fabric buying unit is chosen separately.

Quilt width (in)Quilt length (in)

Usable fabric width (in)Measure after removing selvages and any prewashing. Use the width you can actually cut.

Extra backing on each side (in)Ask your quilter for their required overage. Four inches is an editable example.Seam allowance per edge (in)Each panel join consumes two seam allowances.

May the fabric be turned sideways?

Buying your fabric

Fabric sold byShop cutting incrementFor example, 0.25 yards or 0.10 metres. Confirm with your shop.

Price per selected buying unit (optional)Currency

Working out your fabric…

Shared links contain measurements and prices. No account or saved plan record.

TRY THE NUMBERS

Example: backing a 60 × 80 inch quilt

Start with a 60 × 80 inch quilt, 4 inches of overage per side, 42 inches of usable fabric width, and a 0.5 inch seam allowance on each joined edge.
The backing target is 68 × 88 inches. Two 42-inch panels joined with a 0.5-inch seam allowance provide 42 + 42 − 1 = 83 inches of usable joined width.
Cut two panels, each 88 inches long. Total fabric length is 176 inches, or about 4.89 yards; buying in quarter-yard steps rounds this up to 5 yards.

Overage is added on each side, not once overall. Measure usable fabric after removing selvages, and check your quilter’s requirements before buying.

Open this example in the calculator

Opening the example loads these sample values in place of your current entries.

How to measure

Measure the quilt top edge to edge: A is 60 inches wide and B is 80 inches long. The outer dashed rectangle adds 4 inches on every side, giving a 68 × 88 inch backing target.Illustration only; not drawn to scale.

THE MATH, MADE SIMPLE

From quilt top to backing

Backing size = finished quilt dimensions plus twice the per-side overage. Joined span = panels × usable fabric width − (panels − 1) × twice the seam allowance.

We choose enough panels to cover the required span, then multiply panels by their full cut length. When rotation is allowed, both directions are compared. This is a simple full-width panel plan, not an optimized scrap-piecing pattern.

Before you cut

Confirm your quilter’s backing and batting requirements. Measure usable fabric after selvages and prewashing. Directional prints, repeat matching and squaring up may need more fabric.

Read the fabric planning guide ↗