How much fabric for quilt backing
Make the backing about 4″ bigger than the quilt top on every side. Divide the backing's width by the usable width of your fabric (40″), round up to get the number of lengths, then multiply by the backing's length. A 62 × 76″ throw needs a 70 × 84″ backing: two lengths of 84″, 168″, 4¾ yd. Try the seams both ways and keep the cheaper one.
Plan it in your own fabrics with Sashing →
Why the backing is bigger than the top
Quilting pulls the layers in, and a longarm frame needs fabric to hold on to. So the backing and batting are cut larger than the top. Four inches on every side (8″ added to each measurement) is a common allowance and the one Sashing uses. If a longarm quilter is finishing your quilt, ask what they want first. Some ask for more.
How many lengths of fabric
Standard quilting cotton is narrower than almost any backing, so the backing is pieced from lengths sewn side by side:
- Backing size = top + 8″ each way. A 62 × 76″ throw: 70 × 84″.
- Lengths needed = backing width ÷ usable width, rounded up. 70 ÷ 40 = 1.75, so 2 lengths.
- Fabric = lengths × backing length. 2 × 84″ = 168″, which is 4.67 yd, rounded up to 4¾ yd.
Vertical or horizontal seams: check both
You can also turn the lengths sideways and run the seams across the quilt. Work it out both ways and keep the smaller number. For a queen, 90 × 104″, the backing is 98 × 112″:
- Seams running down: 112″ is the length, 98 ÷ 40 rounds up to 3 lengths, so 336″ (9⅜ yd).
- Seams running across: 98″ is the length, 112 ÷ 40 rounds up to 3 lengths, so 294″ (8¼ yd).
Running the seams across saves 1⅛ yd on this quilt. Sashing tries both directions and shows the cheaper one, for example “two 84″ lengths”.
Backing by quilt size
For the five size presets in Sashing, laid out with 12″ Ohio Stars, 2″ sashing and a 4″ border (see the quilt sizes chart), at 40″ usable width:
| Quilt | Backing | Lengths | Buy |
|---|---|---|---|
| Crib 34 × 48″ | 42 × 56″ | 2 × 42″ | 2⅜ yd |
| Throw 62 × 76″ | 70 × 84″ | 2 × 84″ | 4¾ yd |
| Twin 76 × 90″ | 84 × 98″ | 3 × 84″ | 7 yd |
| Queen 90 × 104″ | 98 × 112″ | 3 × 98″ | 8¼ yd |
| King 104 × 104″ | 112 × 112″ | 3 × 112″ | 9⅜ yd |
These are worked with Sashing's rules: 4″ overhang, 40″ usable width, rounded up to ⅛ yd. They are not taken from a published pattern, and a pattern that plans on 42″ or adds a margin will give different numbers.
Wide backing instead
Wide backing fabric, often 108″ wide, covers most quilts in one piece with no seams. You buy just the backing's length (or its width, whichever is smaller once it fits). Sashing's backing line assumes ordinary-width fabric, so if you use a wide back, measure the backing and buy its length directly.
The rest of the edge
With the backing sorted, the binding is the last fabric to plan: how to calculate quilt binding. For the whole quilt's list, see how much fabric for a throw quilt.
Sashing
A quilt design app for Android. Lay out classic blocks with sashing and borders in photos of your own fabrics, then get the finished size, the yardage for every fabric and a cutting chart with the ¼″ seams added. Designing and seeing the quilt is free; the yardage, cutting chart and PDF are part of Sashing Pro, a subscription with a 3-day free trial.