Quilt backing calculator
Buy 5.00 yd of backing fabric and cut it into lengths of 88.0 in. The backing has to measure 68.0 in by 88.0 in; with the seams the other way it would take 5.67 yd.
Result
Backing fabric to buy
yd
Exact length needed
yd
Panels to cut
pcs
Length of each panel
in
Backing width
in
Backing length
in
Needed with the seams the other way
yd
How it works
The backing is the quilt top plus extra on every side, because quilting draws the layers in and a longarm frame needs something to hold. Standard quilting cotton is too narrow for most quilts, so the backing is pieced from panels: the tool counts how many widths cover the backing, once with the seams running along the quilt and once across it, and takes the shorter cut. That answers how much backing fabric you need for a quilt of your own size, where a quilt backing yardage chart only lists a few beds. For backing fabric for a queen size quilt, pick the queen example and compare it with wide backing fabric yardage in the next example.
Formula
backing width = quilt width + 2 × extra; backing length = quilt length + 2 × extra. Panels = the fewest fabric widths that cover the backing once each seam has taken one seam allowance from both panels. Seams along the length: fabric = panels across the width × backing length. Seams across the width: fabric = panels along the length × backing width. The shorter total is used unless you pick a direction, and it is rounded up to the buying step.
Worked example
The calculator opens with this example; the result above is computed from it.
| Input | Value |
|---|---|
| Quilt top width | 60 in |
| Quilt top length | 80 in |
| Extra on each side | 4 in |
| Usable fabric width | 40 in |
| Seam direction | Whichever uses less fabric |
| Seam allowance between panels | 0.5 in |
| Round the amount up to | The next quarter yard |
| Backing fabric to buy | 5.00 yd |
| Exact length needed | 4.89 yd |
| Panels to cut | 2 pcs |
| Length of each panel | 88.0 in |
| Backing width | 68.0 in |
| Backing length | 88.0 in |
| Needed with the seams the other way | 5.67 yd |
Common cases
| Case | Starting values | Backing fabric to buy | Exact length needed | Panels to cut | Length of each panel | Backing width | Backing length | Needed with the seams the other way |
|---|---|---|---|---|---|---|---|---|
| Throw quilt on standard cotton | Quilt top width 50 in; Quilt top length 65 in; Extra on each side 4 in; Usable fabric width 40 in | 3.25 yd | 3.22 yd | 2 pcs | 58.0 in | 58.0 in | 73.0 in | 4.06 yd |
| Queen quilt on standard cotton | Quilt top width 90 in; Quilt top length 95 in; Extra on each side 4 in; Usable fabric width 40 in | 8.25 yd | 8.17 yd | 3 pcs | 98.0 in | 98.0 in | 103.0 in | 8.58 yd |
| Queen quilt on wide backing fabric | Quilt top width 90 in; Quilt top length 95 in; Extra on each side 4 in; Usable fabric width 104 in | 2.75 yd | 2.72 yd | 1 pcs | 98.0 in | 98.0 in | 103.0 in | 2.86 yd |
| Baby quilt | Quilt top width 36 in; Quilt top length 52 in; Extra on each side 4 in; Usable fabric width 40 in | 2.50 yd | 2.44 yd | 2 pcs | 44.0 in | 44.0 in | 60.0 in | 3.33 yd |
| King quilt for a longarm quilter | Quilt top width 108 in; Quilt top length 95 in; Extra on each side 5 in; Usable fabric width 40 in | 8.75 yd | 8.75 yd | 3 pcs | 105.0 in | 118.0 in | 105.0 in | 9.83 yd |
Questions and answers
How much backing fabric do I need for a queen size quilt?
A queen quilt top of 90 in by 95 in needs a backing of 98.0 in by 103.0 in. On fabric with 40 in of usable width that is 8.25 yd, cut into lengths of 98.0 in and sewn side by side.
How much wide backing fabric do I need for a queen quilt?
On wide backing with 104 in of usable width, a top of 90 in by 95 in needs no seam at all: buy 2.75 yd.
How much backing fabric do I need for a baby quilt?
A baby quilt top of 36 in by 52 in needs a backing of 44.0 in by 60.0 in. That is 2.50 yd of fabric with 40 in of usable width, cut into lengths of 44.0 in.
Assumptions and limits
- Fabric sold as forty-two to forty-four inches wide gives about forty inches once the selvages are off. Measure yours if the count of panels is close.
- The extra is added on all four sides. Check what your quilter asks for before you cut.
- Every seam between two panels takes one seam allowance from each panel.
- A directional print or a wish to avoid a seam down the middle can decide the direction for you; pick it instead of the shortest cut.
The result is an estimate for planning, not professional advice.
Sources
- Missouri Star: how to figure yardage for quilt backing (add 8 in, divide by 40 in usable, round up to a quarter yard; worked example and chart)retrieved 2026-10-13
- Mrs Quilty: quilt backing fabric calculation (8 to 10 in of overage per dimension)retrieved 2026-10-13
Last updated:
Method in depth: Quilt backing: panels, seams and overage
Cite this page: Quilt Math, “Quilt backing calculator”, https://quilt-math.pages.dev/backing-and-binding/quilt-backing-calculator/ (updated 13 October 2026).
Found a mistake? Email handycalc.sites+quiltmath@gmail.com.