Backing is sized to the frame, not to the quilt
A backing is not the same size as the top. It has to extend past the top on all four sides so the quilting frame has something to clamp and so the layers can shift slightly without running off the edge. How much extra is a requirement set by whoever is doing the quilting, not a property of the quilt. Three to four inches per side is what many longarm quilters ask for; some ask for more, a few work happily with less, and a domestic machine quilter basting on a table may want only an inch or two of insurance.
Ask before you cut. This is the one number on the page you should not take from a calculator, because a backing that arrives two inches short does not get quilted that day.
The seam question, and why 108 inch goods exist
Standard quilting cotton is 44 to 45 inches on the bolt, of which about 42 to 43 inches is usable once the selvages come off. Any backing wider than that needs at least one seam, and at that point the arithmetic changes shape: you stop buying the width of the quilt and start buying a whole extra length of fabric for each additional panel.
| Backing needed | On 44" goods | On 108" goods |
|---|---|---|
| Up to about 42" | 1 width, no seam | 1 width, no seam |
| 43 to 82" | 2 widths, 1 seam | 1 width, no seam |
| 83 to 122" | 3 widths, 2 seams | 1 width across, no seam |
The 108 inch column is why extra-wide backing is worth the higher price per yard on anything bigger than a lap quilt. On a 60 by 80 top with 4 inch overhang you need a 68 by 88 backing: that is two and a half yards of 108 inch goods with no seam at all, against roughly five yards of 44 inch goods plus a seam to piece. Run the numbers with your actual prices before assuming the cheap-per-yard option is cheaper overall.
Which way to run the seam
When you do need two widths, you can run the seam down the length or across the width, and the yardage is usually different. This calculator picks the cheaper one and shows you the other so the decision stays yours, because it is partly an appearance decision. A horizontal seam across the middle of a bed quilt lands where a sleeper's knees go; a vertical one runs down the centre of the back.
The common workroom dodge is to avoid a centre seam entirely: take the second width, cut it in half lengthwise, and sew a half to each side of a full-width centre panel. Two seams instead of one, the same yardage, and the back reads as a deliberate three-panel design instead of a join. Press backing seams open rather than to one side; a pressed-open seam is half the bulk for a longarm needle to cross.
Binding: the two numbers that are conventions, not facts
Double-fold binding, often called French binding, is a strip folded in half lengthwise, sewn to the front through both raw edges, then folded over the edge and finished on the back. The strip therefore has to wrap the front, the thickness, and the back, plus the seam allowances that get buried.
The usual formula is cut width equals four times the finished width plus twice the seam allowance. Half inch finished at a quarter inch seam gives a 2.5 inch cut strip, which is the width most people cut without thinking about it. But four is a convention, not a constant. Quilters who like a tightly filled binding use 4.25 or 4.5 because a thick batting takes up more strip in the wrap than the flat arithmetic predicts. Thin batting and a firm press can go the other way. The multiplier is an input here for exactly that reason: cut a test strip on a scrap sandwich of your actual batting before you cut forty feet of it.
The corner allowance is the other soft figure. Each mitred corner consumes a little length, and the two ends have to be joined to each other, which needs overlap. Ten to twelve inches total is what most people add. If you join your strips with diagonal seams rather than straight ones, each join also consumes roughly the strip width off the usable length, which is what the strip length figure above accounts for.
What is not in here
Batting is not calculated on this page. It follows the same overhang logic as the backing and is usually bought by the packaged crib, twin, queen or king size or off a wide roll, so the sizing question is which package to buy rather than how many inches to cut. Nor is the quilt top itself: the piecing yardage depends on your block, and the fabric yardage calculator will handle it if you can list the cut pieces.
If you want binding cut on the bias rather than across the grain, the strip length available from a given piece of fabric works differently, and the bias binding calculator covers it. Bias is worth the trouble on curved edges and on striped or plaid fabric; on a straight-edged quilt, cross-grain strips are the normal choice.
One thing to be careful about: if the quilt is intended for an infant, safe sleep and infant bedding are regulated safety topics and the guidance changes. Do not take sizing or use advice for that from a craft calculator, this one included. Check the current guidance from the U.S. Consumer Product Safety Commission and your pediatrician instead.
Questions people ask
How much backing fabric do I need for a queen quilt?
Work it from your own top size rather than the bed name, because quilt sizes labelled queen vary by a foot. As an illustration, a 90 by 96 top with 4 inch overhang needs a 98 by 104 backing. On 44 inch goods that is three widths at 104 inches each, close to nine yards. On 108 inch goods it is one width run crosswise, under three yards. Enter your actual measurements above and the seam plan comes out with the yardage.
What width should I cut quilt binding?
Two and a half inches is the default most quilters use, and it produces roughly a half inch finished double-fold binding at a quarter inch seam. That is a convention rather than a rule. Thicker batting fills more of the wrap and can leave a 2.5 inch strip feeling tight, so some people cut 2.25 for thin batting and 2.75 for a puffy one. The reliable method is to make a test sandwich from the actual batting and backing you are using, bind six inches of it, and look at the result before cutting the rest.
How many binding strips do I need?
Divide the perimeter plus about ten to twelve inches by the usable length of one strip. A 60 by 80 quilt has a 280 inch perimeter; add 12 and you need 292 inches. From 44 inch goods, after trimming selvage and losing about the strip width to each diagonal join, a strip yields roughly 40 usable inches, so eight strips. Eight strips at 2.5 inches is 20 inches of fabric, a little over half a yard.
Do I have to prewash backing fabric?
It depends on what you want the finished quilt to look like. Prewashing everything means the quilt comes out of its first wash the size it went in. Not prewashing means the cotton shrinks around the quilting lines and gives the crinkled, antique look many people are after — but only if the top, batting and backing shrink at similar rates. Mixing a prewashed backing with an unwashed top is the combination that causes trouble, because the two layers move differently. Pick one approach and apply it to everything in the quilt.
Can I use a bed sheet as quilt backing?
People do, and it removes the seam, but be aware of the trade-offs before you commit forty hours of piecing to it. Sheeting is usually a higher thread count and a tighter weave than quilting cotton, which makes hand quilting hard work and can be tough on a longarm needle. Percale and sateen also behave differently under tension on a frame. Ask your quilter first, because some decline sheet backings outright, and finding that out after you have basted is expensive in time.