Quilt Backing Calculator
Find exactly how much backing fabric to buy, which way to seam it, and print a cut diagram.
Fabric to buy
Updates as you typeQuilt Backing Calculator · Cut list
Your cutting plan
Drawn to scaleHow it works
Allow for overhang, then compare panels
Add your overhang to all four sides of the quilt. Then we compare full-width fabric panels joined side by side with panels stacked top to bottom.
Each join uses two seam allowances, one from each panel. We choose the direction that uses the least fabric. On a tie, we pick fewer seams, then vertical.
Backing length = quilt length + 2 × overhang
For a dimension D, usable width U, and seam allowance a: use one panel if U ≥ D. Otherwise, round (D − 2a) ÷ (U − 2a) up to a whole panel. Multiply panels by cut length, add the shrinkage percentage, then round the purchase up to 1/8 yard or 0.1 meter.
Example: a 60 × 72 inch throw
With 4 inches of overhang, your backing needs to be 68 × 80 inches.
Using 40-inch usable fabric and a 1/2-inch allowance per edge:
Vertical: 2 panels × 80 inches = 160 inches. Buy 4 1/2 yd (4.1 m).
Horizontal: 3 panels × 68 inches = 204 inches. Buy 5 3/4 yd (5.2 m).
The vertical plan uses less fabric and has one seam. Its 11-inch leftover strip can often become binding.
Frequently asked questions
How much bigger than the quilt top should the backing be?
Start with 4 inches on every side, making the backing 8 inches wider and 8 inches longer than the quilt top. Longarm quilters often want 4–6 inches per side; ask your quilter for their requirements before buying or cutting.
Should I seam my backing vertically or horizontally?
The calculator recommends the direction that uses less total fabric before purchase rounding. If both use the same amount, it chooses fewer seams, then vertical. Your quilter’s loading requirements or a directional print may make the other option a better choice.
How much 108-inch wide backing do I need?
Choose “Wide-back 108 inch.” We start with 104 inches of usable width to allow for selvages, but you can edit it. If your required backing width fits, one panel cut to the backing length is enough. A wider quilt can still require a seam. Measure the fabric’s actual usable width.
Do I need to prewash backing fabric?
Follow the fabric maker’s care instructions and your quilter’s advice. If you prewash, enter a shrinkage percentage to add that percentage to the total fabric length you buy. This is an extra-yardage allowance, not an exact prediction of shrinkage. Enter the expected usable width after washing and allow separately for print matching.
How do I calculate backing for a queen-size quilt?
Select the typical Queen preset of 90 × 108 inches, then replace it with your actual quilt measurements. With 4 inches of overhang, the backing is 98 × 116 inches. At 104 inches usable wide-back width and no added shrinkage, one 116-inch panel needs 3 1/4 yards (3.0 meters).
Can I use the leftover backing for binding?
Often, yes. The calculator shows the strip left after joining the panels and trimming to your required backing size. Whether it is enough for binding depends on your binding strip width, quilt perimeter, joins, grain direction, and any shrinkage or trimming. Save the scraps and measure before cutting.
Why do you round up to 1/8 yard?
Rounding up turns the calculated length into a practical purchase amount and helps avoid buying less than you need. Some shops sell in larger increments, so round up again to their next increment. Add extra for pattern matching, squaring uneven ends, or other cutting needs.
Does the calculator work in centimeters?
Yes. Switch to centimeters/meters to enter dimensions in centimeters and see meters as the main purchase amount. Calculations run internally in inches. Yardage is rounded up to 1/8 yard and meters independently to 0.1 meter, so the two rounded purchase amounts may differ slightly.