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Quilt Backing Calculator

Enter your quilt size and fabric width to get exact yardage, panel count, and cutting instructions — for standard or wideback fabric.

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Your results

Yardage to buy5 yd
Cutting instructionCut 2 panels, each 88″ long. Join along the long edges.
Panels needed2
Backing size needed68″ × 88″

How the backing yardage calculation works

Quilt backing needs to extend beyond the quilt top on all four sides — typically 4 inches per side — so the longarm quilter or home machine has enough fabric to load, pin, and maneuver without the edges pulling tight. The calculator adds this overage to your quilt dimensions, then figures out how many full-width panels you need to cover the required backing width, and how much fabric to buy.

Panels run the full height of the backing and are placed side-by-side. If your backing needs to be 68 inches wide and your fabric is 42 inches wide, you need two panels — one panel does not cover, but two panels (84 inches joined) more than cover with seam allowance. The calculator always rounds up to the next full panel.

Standard WOF vs. wideback: which should you choose?

Decision guide

Quilt is a baby, crib, or small lap size
Standard WOF (42–44″)
Usually needs only 1–2 panels; standard fabric is cheapest.
Quilt is a throw or twin
Either works
Standard needs 2 panels with one seam; wideback eliminates the seam.
Quilt is a queen or king
Wideback (108″) is often worth it
Standard needs 3 panels and 2 seams; wideback is seamless up to ~100″ wide.
You want a scrappy or pieced backing
Standard WOF
Use up stash fabric; the seam becomes a design feature.
You're sending to a longarm quilter
Ask your longarmer
Some prefer no centre seam; others charge extra for wideback loading.

Panel orientation: how the pieces go together

Understanding panel orientation prevents cutting mistakes. Here is how it works for a standard two-panel backing (e.g., a throw quilt with 42-inch fabric):

  ← Backing width needed (e.g. 68″) →

  ┌────────────────┬────────────────┐  ↑
  │                │                │  │
  │   Panel 1      │   Panel 2      │  │  Panel length
  │   (42″ wide)   │   (42″ wide)   │  │  = backing height
  │                │                │  │  (e.g. 88″)
  │                │                │  │
  └────────────────┴────────────────┘  ↓
        ↑
  Join seam here — sew panels along
  the long edges, press seam open
Two-panel standard WOF backing — panels run full height, joined side-by-side

Cut both panels to the same length (the backing height), sew them together along one long edge with a 1/2-inch seam, and press the seam open. Pressing open distributes bulk evenly and prevents a raised ridge that can show through light-coloured quilt tops.

For a three-panel backing (queen or king), the centre panel is full-width and the two outer panels are trimmed to fill the remaining width. Many quilters prefer to cut the centre panel to the exact required width and split the remaining fabric for the two sides, which places both seams symmetrically off-centre — avoiding a seam running down the middle of the quilt back.

Worked examples: crib to king

These calculations use the defaults: 42-inch standard WOF, 4-inch overage per side. The wideback column shows the yardage saving when switching to 108-inch fabric.

SizeQuilt dims42″ WOF108″ Wideback
Crib36″ × 50″3 1/4 yd (2 panels)1 5/8 yd (1 panel)
Throw60″ × 80″5 yd (2 panels)2 1/2 yd (1 panel)
Queen90″ × 108″9 3/4 yd (3 panels)3 1/4 yd (1 panel)
King108″ × 108″9 3/4 yd (3 panels)6 1/2 yd (2 panels)

Wideback fabric typically costs $15–25/yd vs $10–15/yd for standard cotton, but the yardage savings on large quilts often offsets the price difference.

Frequently Asked Questions

How much overage should I add to quilt backing?
4 inches per side (8 inches total in each direction) is the quilting standard. This gives your longarm quilter or home machine enough backing to load and maneuver without running short at the edges. If you are sending the quilt to a professional longarm service, check their requirements — many ask for 6 to 8 inches per side, especially for larger quilts.
What is the difference between standard WOF and wideback fabric?
Standard quilting cotton comes off the bolt at 42 to 44 inches wide (width of fabric, or WOF). Wideback fabric is woven at 108 inches wide — roughly 2.5 times wider. Wideback typically needs only one panel for quilts up to a king size, eliminating the centre seam that standard WOF backing requires. It costs more per yard but saves time and often results in less total fabric because you avoid the overlapping seam allowance between panels.
Which way do the backing panels run?
Panels run the full length (height) of the backing and are joined side-by-side to cover the required width. This is the standard orientation. It places any seam(s) vertically down the back of the quilt rather than horizontally across it, and means each panel is cut to the same length — making it easy to cut multiple panels from one continuous piece of fabric.
Can I piece backing from scraps instead of buying yardage?
Yes — the key number is the required backing size, shown in the results. Your pieced backing just needs to be at least that wide and that tall. Many quilters piece a scrappy backing using leftover top fabrics, which uses up stash and adds character to the finished quilt. Just make sure all seams are pressed open or to the side (not pressed up) so they lie flat under the quilting.
Do I need to pre-wash backing fabric?
Most quilters pre-wash backing to prevent shrinkage after the finished quilt is washed. Cotton typically shrinks 3 to 5 percent. For a throw quilt with 5 yards of backing, that is up to 7 or 8 inches of shrinkage — enough to pull the edges tight. Pre-washing also removes any sizing or chemicals from the manufacturing process that can affect how the fabric quilts.

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