How to Calculate Quilt Backing and Binding
How much backing fabric do I need?
Your backing needs to be larger than the quilt top on every side — 4″ per side if a longarm quilter is doing the quilting, 2″ per side for a home machine. Add the overhang to your quilt’s width and length, then divide by the usable width of your fabric (fabric width minus about 2″ of selvage) to find how many panels you need. Multiply panels by the panel length and divide by 36 for yards. The calculator above does this in both seam directions and picks the layout that wastes less fabric.
Quilt backing yardage chart
Quick reference with a 4″ overhang per side, comparing standard 42″ quilting cotton against 108″ wideback:
| Quilt size | Dimensions | 42″ cotton | 108″ wideback |
|---|---|---|---|
| Crib | 36 × 52 | 2.5 yd (2 panels) | 1.25 yd |
| Throw | 50 × 65 | 3.25 yd (2 panels) | 1.75 yd |
| Twin | 70 × 90 | 5.5 yd (2 panels) | 2.25 yd |
| Full | 84 × 90 | 7.75 yd (3 panels) | 2.75 yd |
| Queen | 90 × 95 | 8.25 yd (3 panels) | 2.75 yd |
| King | 110 × 108 | 9.75 yd (3 panels) | 6.5 yd (2 panels) |
Wideback usually wins on both cost and quality for anything larger than a throw — no seams to press, no pattern matching.
Binding math, briefly
Binding length = quilt perimeter plus about 10″ for turning corners and joining the ends. Divide that by your fabric’s usable width to get the number of strips, then multiply strips by strip width for the total fabric needed. A queen quilt (370″ of perimeter plus joins) needs 10 strips of 42″ fabric at 2.5″ wide — about 0.75 yards. Cut strips selvage to selvage and join them at 45° angles to spread the seam bulk.
Mistakes that waste fabric
- Forgetting the selvage: 42″ fabric gives you roughly 40″ of usable width once selvages are trimmed.
- Measuring the pattern size instead of the finished top — borders and sashing change the final dimensions. Measure the actual quilt top.
- Buying backing before the longarmer confirms their overhang requirement.
- Prewashing the top but not the backing (or vice versa) — mismatched shrinkage puckers the quilt at the first wash.
Pro tip: When a calculation lands close to a panel boundary (say your backing needs 41″ of usable width from 42″ fabric), buy the next quarter yard up or step up to wideback. Fabric shrinks about 3-5% in the wash, and an inch short is a seam you didn’t plan for.
Frequently Asked Questions
How much backing fabric do I need for a queen quilt?▼
A 90 x 95 inch queen quilt with 4 inches of overhang per side needs a 98 x 103 inch backing. With standard 42-inch quilting cotton that means 3 panels — about 8.25 yards. With 108-inch wideback fabric a single panel works — about 2.75 yards. Wideback almost always costs less per quilt and has no seams.
How wide should quilt binding strips be?▼
2.5 inches is the standard for double-fold (French) binding on quilts with regular batting. Use 2.25 inches for a tighter binding or thin batting, and 2.75 to 3 inches for thick or double batting. All widths are cut selvage to selvage.
How much extra backing do longarm quilters need?▼
Most longarm quilters ask for 4 inches of extra backing on every side (8 inches total in each direction) so the backing can be loaded onto the frame rollers. If you quilt on a home machine, 2 inches per side is enough. Always confirm with your longarmer before cutting.
Should backing seams run vertically or horizontally?▼
Whichever direction wastes less fabric — this calculator checks both and tells you the cheaper layout. For bed quilts, horizontal seams are often preferred because they end up parallel to the roller bars on a longarm frame, which reduces sagging.