Quilt backingcalculator
Enter your quilt size and the fabric you plan to use. You get the yardage to buy, how many panels to cut, where the seams go, and a drawing of the layout.
QuiltHelperEnter a quilt width and length greater than zero.
Fabric to buy
37⁄8yards
Exact: 3.78 yards, rounded up to the next 1/8 yard
Cut 2 panels of 42" fabric, each 68" long, and sew them together along the long edges with a ½" seam. The seams run side to side.
Compare layouts
Same quilt, same extra on each sideCutting layout
Backing yardage for common quilt sizes
With 4" of extra backing on every side. "42" cotton" uses whichever seam direction needs less fabric.
Swipe the table sideways to see every column.
| Quilt | Quilt top | Backing size | 42" cotton | Panels & seams | 108" wideback |
|---|---|---|---|---|---|
| Baby | 36" × 48" | 44" × 56" | 21⁄2 yd | 2, horizontal | 11⁄4 yd |
| Throw | 50" × 65" | 58" × 73" | 31⁄4 yd | 2, horizontal | 15⁄8 yd |
| Lap | 60" × 72" | 68" × 80" | 37⁄8 yd | 2, horizontal | 2 yd |
| Twin | 70" × 90" | 78" × 98" | 51⁄2 yd | 2, vertical | 21⁄4 yd |
| Queen | 90" × 108" | 98" × 116" | 81⁄4 yd | 3, horizontal | 31⁄4 yd |
| King | 108" × 108" | 116" × 116" | 93⁄4 yd | 3, horizontal | 61⁄2 yd |
How to use this calculator
- Measure the quilt top. Measure the width and length through the middle, from edge to edge. Or pick one of the common sizes.
- Choose your backing fabric. Standard quilting cotton is about 42" wide once the selvages are trimmed. Wideback is sold 108" wide.
- Set the extra on each side. 4" is the usual request from longarm quilters. Use less for hand or home-machine quilting.
- Read the result. Buy the yardage shown, cut the number of panels at the length shown, and sew them together along the long edges with a ½" seam.
How the backing math works
The backing has to be bigger than the quilt top by the extra you choose on every side. If the fabric is narrower than the backing, you sew panels side by side, and each seam uses up 1" of width (½" from each panel).
Backing width = quilt width + 2 × extraBacking length = quilt length + 2 × extraPanels = (backing span − 1") ÷ (fabric width − 1"), rounded upYards = panels × panel length ÷ 36, rounded up to the next 1/8 yardExample: a 60" × 72" lap quilt on 42" cotton, 4" extra.
The backing must be 68" × 80".
Vertical seams: 2 panels, each 80" long = 41⁄2 yards.
Horizontal seams: 2 panels, each 68" long = 37⁄8 yards.
Horizontal seams save 5⁄8 yard, so the calculator recommends them for this quilt.
Vertical or horizontal seams?
Vertical seams run from the top of the quilt to the bottom. Horizontal seams run from side to side. The direction changes how long each panel is, so one direction often needs noticeably less fabric, as in the example above.
If you quilt on a home machine, choose whichever uses less fabric. If a longarm quilter is finishing your quilt, ask first. Many prefer seams that run parallel to the rollers, so the extra bulk of the seam rolls up evenly. Use the seam direction buttons to see the yardage for the direction they ask for.
When 108-inch wideback is worth it
Wideback fabric is woven 108" wide for quilt backs. For most quilts up to about 96" wide it needs no seam at all, and the yardage is far lower. A queen quilt needs 81⁄4 yards of 42" cotton but only 31⁄4 yards of wideback.
Wideback usually costs more per yard and comes in fewer prints, so compare the total price. The calculator treats about 104" of it as usable, because the selvages and any off-grain edge are trimmed away.
Common backing mistakes
- Using the full bolt width. 44" fabric is not 44" usable once the selvages are cut off.
- Forgetting the seam allowance. Two 42" panels joined with a ½" seam make 83", not 84".
- Not asking your longarm quilter. Some need 6" or more on every side.
- Directional prints. If the print has a clear up and down, the seam direction may be decided for you. Check the yardage for that direction.
- Shrinkage. If you pre-wash, measure after washing.
Questions about quilt backing
How much backing do I need for a queen size quilt?
For a 90" × 108" queen quilt with 4" of extra backing on every side, you need 81⁄4 yards of 42" quilting cotton (3 panels with horizontal seams), or 31⁄4 yards of 108" wideback. Queen quilts vary, so enter your own measurements above.
How much bigger should backing be than the quilt top?
Most quilters add 4" on every side, which is 8" in total to the width and to the length. Longarm quilters often ask for 4" to 6" so the backing can be clamped to the frame. Hand and home-machine quilters sometimes use 2"–3". Ask your longarm quilter before you buy.
Should backing seams run vertically or horizontally?
For quilting on a home machine, either direction works, so pick the one that uses less fabric. Many longarm quilters prefer seams that run side to side, parallel to the rollers, because the seam rolls up evenly. The calculator shows both so you can choose.
Why does the calculator use 42" instead of 44"?
Quilting cotton is sold 42"–44" wide including the selvages. Once the selvages are trimmed, about 40"–42" is usable. 42" is a safe default; if your fabric measures narrower, choose a narrower option or add extra margin.
Do I need to pre-wash backing fabric?
It is a personal choice. If you pre-wash, cotton can shrink by around 2%–5%, so measure the fabric after washing, or buy a little more than the calculator suggests.
Other calculators
How we check this calculator: the formulas above are tested against hand-worked results for standard quilt sizes and for quilts wider than one panel of fabric, and thousands of random sizes are checked to make sure the backing always covers the quilt. Fabric amounts always round up. Last checked November 2026.