Quilt Backing: How Much Fabric, How to Cut It, and the One Seam That Holds It Together

There is one seam between you and a finished quilt, and quilters put it off for weeks.

Not because it is hard. Because it is the least interesting part of the whole project, it happens after the fun is over, and it involves wrestling several yards of fabric across a table that is too small. The quilt top is done. The exciting decisions are all behind you. What is left is arithmetic and a straight line.

Kim of Ma Tante Quilting opens her tutorial by admitting exactly this. She had just finished a quilt top, she needed to make the backing, and she did not want to. Her words: she literally only needed to sew one seam, and for some reason it is a task she always puts off.

If that is you, the good news is that the whole job takes about half an hour once you know the numbers. The numbers are the part that stops people, so this guide starts there and then walks the rest of it: choosing the fabric, cutting the two pieces, the seam, the selvage, the pressing, and the squaring up that your longarm quilter will quietly thank you for.

The video below is the whole process at normal speed, from a quilter who also loads other people's quilts onto a longarm for a living, which is why her advice about what a backing should look like when it arrives is worth more than most.

What a quilt backing actually has to do

Before the arithmetic, it helps to know what you are building, because it changes what you choose.

Karen Brown of Just Get it Done Quilts lays out three jobs, and the second one is the one most people have never thought about.

It encloses the batting. The obvious one. Even without batting, the backing protects the quilt top and stops the seams fraying.

It is the flat layer everything else conforms to. This is the important one. A quilt top can have a wave or two that you massage in while you quilt. The back cannot. Whatever shape the back is in, the finished quilt will follow it.

It has to be soft against skin. You can build the most beautiful quilt in the world, and if the back is scratchy nobody will want to sit under it. Quilts end up on beds and couches with people tucked underneath, and the back gets flipped over more often than the front gets admired.

Those three jobs decide almost everything below. Flat is why the seam allowance is wide and the pressing matters. Soft is why the fabric choice is not just about color.

How much bigger than the quilt top

This is the question, and the answer depends entirely on who is quilting it.

If it is going to a longarm quilter, add four inches on every side. That means the backing is eight inches wider and eight inches taller than the quilt top. The reason is mechanical: the backing has to be attached to the frame, and the quilter needs room at the sides to attach it there too and to sew off the edge of the quilt top. This is not a comfort margin, it is clearance the machine requires.

Both Ma Tante Quilting and the National Quilters Circle give the same figure, four to five inches per side.

If you are quilting it yourself on a domestic machine, two inches a side is enough. Four inches wider and four inches taller overall. You still want the margin, because the layers shift against each other while you quilt and the top grows relative to the bottom, but you do not need clearance for a frame.

Karen Brown is candid about what happens when you cut it fine. She has tried to get away with less and sometimes succeeded, but running short is a real problem: you have to stop, find matching fabric, attach it to the back, and sometimes rip out quilting you have already done. The fabric you save is never worth that.

So: quilt top plus eight inches in both directions for a longarm, plus four for a domestic machine. Measure the quilt top first, and measure it properly. If you have not settled on a finished size yet, our quilt size chart works out the drape before you cut anything.

Quilt backing yardage, worked out for you

Here is the method, and then the tables.

Quilting cotton runs about 42 inches wide, and roughly 40 inches of that is usable once the selvages come off. The Quilter's Bible puts it the same way: remember the selvage, and subtract about two inches from the width.

So if the smaller dimension of your backing is under about 40 inches, one length of fabric does it and there is no seam at all. If it is larger, you need two lengths sewn together along the selvages, which gives you about 79 inches in that direction. Larger again and you need three, which gives about 118.

The yardage is then the number of lengths multiplied by the other dimension of the backing, divided by 36.

Both tables below assume 40 usable inches per cut and a half inch seam allowance. If your fabric runs wide, you will have fabric left over, which is a good problem.

Backing yardage for a longarm quilter, four inches a side

Backing yardage for your own machine, two inches a side

Two things worth reading out of those tables.

The first is where the jump happens. A crib quilt on a domestic machine needs one cut and no seam. Add four inches to the width, because it is going to a longarm, and suddenly you need two cuts and nearly twice the fabric. The 40 inch mark is a cliff, not a slope, and it is worth knowing which side of it your quilt sits on before you buy.

The second is the right hand column. At the queen and king end, wide backing is not a convenience, it is a third of the cost.

A worked example, and why the table is conservative

The quilt in the video measured 64 inches wide by 72 inches tall, and it was going to a longarm.

Width first: 64 plus four on each side is 72. So two cuts, each 72 inches long, sewn together along the selvages, gives a piece 72 inches wide. Sewn, that comes to roughly 82 inches in the other direction, which covers the 80 inches the quilt needs with five inches to spare at the top and bottom.

Two cuts of 72 inches is 144 inches, which is exactly four yards. She had bought five.

Our table says four and a half for the same quilt, and the difference is worth explaining rather than hiding. The table assumes 40 usable inches per cut, which is the conservative figure. Her fabric gave her more than that, so two cuts of 72 produced 82 inches instead of 79 and she came out fine. If you know your fabric runs wide, you can cut closer. If you do not know, buy from the table and enjoy the leftover.

She was not sad about the extra yard, and her reasoning is the reasoning of every quilter with a stash: it was 50 percent off, it is a fabric she likes, and it will turn up in something else.

Choosing the backing fabric

Three things decide this, and only one of them is the print.

Buy in big cuts and buy ahead

Ma Tante Quilting's habit is to watch for shops selling deeply discounted five yard cuts, and there is a reason both sides like that deal. The shop makes one cut and moves a lot of fabric. The quilter gets a chunk big enough to back almost anything at a price per yard they would not otherwise see.

She buys prints she likes without a project in mind, on the theory that if she likes it she will eventually make something it goes with. That is exactly what happened with the quilt in the video: the backing was bought months earlier with no plan, and the finished top turned out to have the same oranges and pinks. Not planning is a strategy when the thing you are buying is flexible.

Non-directional is easier

A non-directional print has no up. Scatter prints, all over florals, dots, texture. You can turn the fabric any way you like and nothing looks wrong.

Directional prints have an up, and on a backing that matters twice: once when you sew the two pieces together, and again when you decide which way the seam runs. Christmas trees are the obvious case. Sew two pieces together carelessly and half your trees are upside down.

You can absolutely use directional fabric, and a five yard cut gives you enough to orient the seam either way so the print stays upright. The point is that non-directional is one less decision, and on a backing that nobody will study closely, one less decision is worth something.

The line is fuzzier than it looks. A diamond print technically has a direction, but nobody on earth cares whether the diamonds point up or sideways. Judge it by whether a viewer would notice, not by whether a rule says it has a direction.

Color, and whether you want the quilting to show

Karen Brown makes a point that gets missed: the back is not just a design choice, it is a decision about visibility. Three things control how much your quilting shows on the back.

The contrast of your bobbin thread. More contrast, more visible.

The weight of your bobbin thread. Thicker thread, more visible.

How busy the print is. A busy pattern hides quilting almost completely, and a solid shows everything, including the parts you would rather nobody examined.

That last one cuts both ways. If you have quilted something you are proud of, a quiet back displays it. If you are still learning, a busy print is a friend. And the thread on the back does not have to match the thread on the front, though you do not want a lot of contrast between the two, because bobbin thread occasionally pops through and announces itself.

Whatever you choose, the backing has to be soft. That is the third job, and a fabric that fails it fails the quilt.

Wide backing, and when the seam stops being worth it

There is a way to skip all of this. Backing fabric is made in extra wide widths, and The Quilter's Bible names three: 60 inches, 90 inches and 108 inches.

At 108 inches you can back almost any quilt with a single piece and no seam at all. No cutting two lengths, no pinning, no pressing a seam, no squaring up two pieces that do not quite match. Our 108 inch wide quilt backing comes in three yard cuts in cream, tan, gray, red and black, which covers everything up to a queen in one purchase.

Look again at the right hand columns of those tables. A queen backing is eight and a quarter yards of ordinary quilting cotton, or three and a quarter yards of wide backing. The wide fabric costs more per yard, but you are buying less than half as much of it, and you are buying zero seams.

There is one honest limit. A king quilt needs a backing around 116 inches across, which is wider than 108, so even wide backing needs a seam there.

The seamed method below is still worth knowing. It is what you use when you want a particular print, when you found a deal, and when the quilt is small enough that the difference does not matter.

Cutting the two pieces

This is the part that feels harder than it is, because the fabric is bigger than the table.

Start by trimming the cut end square. Fabric does not leave a shop cut straight, and everything downstream is easier if the first edge is honest. Our guide to cutting fabric accurately covers the checks worth making on the rotary cutter before you start on several yards of anything.

Then measure the length you need. Ma Tante Quilting's trick is the simplest one in the video and it removes the tape measure entirely: her cutting mat is 36 inches wide, so she lays the fabric along the mat, folds it back at the far edge, and lays it out a second time. Two mat widths is 72 inches, and her thumb on the 36 inch line marks the fold. No tape measure, no math, no creeping error.

If your mat is 24 inches, the same trick gives you 48 inches in two passes and 72 in three. The principle is that a fixed reference you can see beats a tape measure you have to hold still with one hand.

Cut along the fold with a long ruler and a rotary cutter, and then repeat for the second piece.

Two notes on accuracy that come straight from the video. The cuts do not need to be perfect. If you are going to be off, be off long rather than short, because long gets trimmed and short gets replaced. And the second cut will usually be slightly less accurate than the first, which is normal and does not matter, because the sides get squared up at the end anyway.

The selvage, and why it does not belong in your seam

This is the detail that separates a backing that lies flat from one that does not, and most quilters have never had it explained.

The selvage is the finished edge of a woven fabric that keeps it from unraveling, and Britannica describes it as a narrow border sometimes made with different or heavier threads than the main fabric, and sometimes in a different weave altogether. That is the whole problem in one sentence: it is thicker, denser, and under a different tension than the fabric beside it.

Sew a quarter inch from the fuzzy edge and you are sewing through selvage. That seam will behave differently from every other seam in the quilt, because it is holding two strips of denser, tighter fabric. It will pull. The Quilter's Bible says the same thing in its instructions for preparing a quilt sandwich: trim off the selvages first, before anything else.

There is a second reason, and it is about what shows. Many selvages carry printed information: the manufacturer's name, the fabric line, the little row of color dots. If you back a quilt in a light fabric and leave a printed selvage inside the seam, you will see it through the backing. On a pale back that printed strip reads clearly from the right side, which is a strange thing to discover after the quilt is finished.

So the rule is: anything colored or printed comes off, and it comes off completely.

There are two ways to get there, and both are used by experienced quilters.

Trim first, then sew. Cut the printed selvage away before you pin, then sew your chosen seam allowance from the clean edge. This is Ma Tante Quilting's approach and it is the easier one to control.

Sew wide, then trim. Karen Brown leaves the selvages on, sews the two pieces together with a one inch seam allowance, and then trims the selvages off afterward. Depending on how wide that particular selvage was, she ends up with a seam allowance somewhere between a quarter and a half inch.

Both end in the same place: no printed selvage inside the quilt. Pick the one that suits how you like to work.

One thing Ma Tante Quilting is firm about, and it is the right priority. If your seam wanders and you end up with a smaller seam allowance than you planned, take the smaller seam allowance. A three eighths inch seam with no printed selvage beats a half inch seam with a stripe of manufacturer's text running down the back of your quilt.

The seam, and why half an inch

Almost everything in quilting is sewn at a quarter inch. This is the exception, and there is a reason.

A backing seam wants to be wide. Ma Tante Quilting sews hers at half an inch, and she sees the alternative constantly, because she loads other people's quilts: backings that arrive with a quarter inch seam, or sometimes an eighth, have a harder time lying flat. A narrow seam allowance on a seam this long does not have enough fabric on either side to settle.

Flat is the whole job of a backing. So half an inch.

Karen Brown's answer is a version of the same thing. She says the seam can be any width you want as long as it is consistent, and then sews at a full inch before trimming. The agreement underneath the two methods is what matters: wider than a quarter, and the same all the way down.

Pin it. Pin every couple of inches along the whole edge. Two pieces of fabric this long have a real tendency to shift against each other as they feed, and pins are what stop the far end from arriving two inches out of true.

When you pin, put one printed selvage against one unprinted selvage rather than two printed ones together. On a directional print this is what keeps both halves running the same way up. It costs nothing to do it on a non-directional print too, and it means you never have to think about which case you are in.

Use a shorter stitch than your usual piecing stitch. Ma Tante Quilting drops to 1.8 or 2.0. Backstitch at both ends. Then sew slowly, letting the machine pull the fabric through rather than pushing it, and keep the edge aligned with a fixed mark on the throat plate. Her own note is that her instinct is to go as fast as humanly possible and that she gets better results when she does not.

Pattern matching across the seam is optional and mostly unnecessary. On a busy print nobody will ever see it. On a large motif, Karen Brown does align and sometimes centers it, and says the extra work showed. Judge it by standing back and looking at the fabric from across the room before you decide.

Press it open, or press it to the side

Here the sources disagree, and the disagreement is instructive rather than confusing.

Press it open. Ma Tante Quilting presses her backing seam open, and knows that some quilters worry about this. Her two reasons are good ones. First, the quilting itself will cross that seam many times when the quilt goes on the machine, which secures it far beyond what the seam alone is doing. Second, she sewed it with a shorter stitch length precisely so it would hold. Between those two, the seam is not going anywhere.

The Quilter's Bible agrees, and in its instructions for preparing a quilt sandwich it says the same thing outright: press seams open.

Press it to the side. Karen Brown always presses to the side. She is not wrong either, and on a seam that has already been trimmed down from an inch there is a practical argument for it.

Open lies flatter, which matters because flat is the job. To the side is stronger at the seam itself, which matters less here than it does in a quilt top, because of the quilting that is about to cross it.

If you are sending the quilt to a longarm quilter, press it open. A backing that lies flat loads better, and you have the quilting to secure the seam. If you are hand quilting and the seam will not be crossed much, either choice is defensible.

The Bible adds one warning here that neither video mentions and that is worth carrying with you. Avoid a seam that runs down the exact center of the quilt. The Canadian Conservation Institute's guidance on quilts is blunt about this: it is best to avoid folding them at all, because the creases may damage the quilt, and when a quilt must be folded they advise re-folding it regularly so the crease keeps moving. A fold that always lands on the same seam is the worst case of that. If you are making a backing from two equal pieces the seam lands in the middle by definition, so on a quilt you expect to be an heirloom, consider cutting the pieces unequally so the seam sits off center.

Squaring it up before it goes anywhere

You will almost certainly find that the two sides do not match when the seam is sewn. A quarter inch, sometimes more. This is normal and it happens for ordinary reasons: the two pieces were not cut identically, or they were not aligned perfectly when pinned, or the fabric shifted a little while sewing, or the original cut from the bolt was not straight.

Take the time to trim it square anyway.

Fold the backing so the seam you just sewed runs parallel to the outside edge, feel along for where the difference is, and trim the overhang off. Do both ends.

This one is worth doing even though nobody will see it, and the reason comes from the other side of the transaction. Ma Tante Quilting loads other people's quilts, and her observation is that most quilters do not know this: a longarm quilter would much rather receive a backing that is squarish. It does not have to be measured on the diagonal. But a backing with a two inch overhang on one side is meaningfully harder to load, because loading starts with finding the center of everything, and finding the center of a crooked rectangle is a job.

Her own trade off is the one to copy. She would rather send a backing that is square and a quarter inch short than one that is big and crooked.

When the seam has to run the other way

The default is a horizontal seam, which is what you get by cutting two lengths and joining them along the selvages. Two situations override that.

A directional print. If the fabric has a clear up, and you want it upright on the finished quilt, orient the pieces so the print runs the right way. On a five yard cut you usually have enough fabric to run the seam vertically instead, from the top of the quilt to the bottom, which keeps the whole print facing the same direction.

A print that runs parallel to the selvage, or a fabric with a nap. Karen Brown's examples are minky and flannel, where the fabric has a direction in its surface rather than its print. These have to be pieced vertically, which means two pieces the height of the quilt plus your margin rather than the width.

That change costs fabric, and sometimes a lot. The National Quilters Circle works a queen sized example both ways: with the seam one direction it comes to seven yards, and with the seam the other direction it comes to almost nine. Same quilt, same margin, two yards of difference. Work it out both ways before you buy and pick the cheaper one, unless the print decides for you.

One more thing from the National Quilters Circle, and it is the sort of advice that saves an awkward conversation. Some longarm quilters prefer the seam running one way, some the other. Ask yours before you cut. It takes a message and it is cheaper than a second backing.

Pieced backings, and one warning

You do not have to use a single fabric. A pieced back is a good home for leftover blocks, orphan half square triangles, partial fat quarters and the strips and crumbs that accumulate beside the machine. The Quilter's Bible describes it as adding an extra dimension to the quilt and a good use of what is left over from the top, and notes that it can be simple strips, large squares, or a combination.

Karen Brown builds these deliberately and calls the result a reversible quilt, on the reasoning that by the time she has finished a top she is finished with that fabric, and the back is the natural place for it to end up. It also means buying less.

Three conditions come with it, and the third is the one to know before you commit.

It still has to lie flat. That is non negotiable and it gets harder, not easier, with more seams in it.

The added bulk makes custom quilting on the top considerably more difficult, because the machine is fighting extra layers in places.

And many longarm quilters will not take a pieced back at all, precisely because of that. If you are planning to send the quilt out, ask first. Finding out after the back is built is the expensive order to do it in.

Download the one page quilt backing reference, free. Both yardage tables on one sheet, at 42 and 108 inch widths, plus the method in four short paragraphs. Made to print and live on the wall above the cutting table.

The whole thing, in order

For when you have read all of the above and just want the sequence.

Measure the finished quilt top, width and height. Add eight inches to each for a longarm, four for your own machine. Look up the yardage in the table, or work it out: if the smaller number is under 40, one length; under 79, two; otherwise three. Multiply the number of lengths by the other dimension and divide by 36.

Buy the fabric, non-directional if you have the choice. Trim the cut end square. Measure and cut your lengths, erring long. Trim the printed selvages off the two edges that will meet, or plan to trim them after sewing.

Pin the two pieces right sides together every couple of inches, printed selvage against unprinted selvage. Shorten the stitch length to about 1.8, backstitch, and sew slowly at a half inch seam allowance the whole way down. Backstitch at the end.

Trim the seam allowance even. Press the seam open. Square up both ends so the outside edges run parallel to the seam. Press the whole piece.

That is a backing. One seam, about half an hour, and the thing you have been putting off for three weeks is behind you.

Common questions

How much bigger should a quilt backing be? Four inches larger on every side for a longarm quilter, which is eight inches in each dimension overall. Two inches a side if you are quilting it yourself, which is four inches overall.

Can I use a bed sheet as a quilt backing? The three jobs are the test: flat, soft, and encloses the batting. A sheet is usually a tighter weave than quilting cotton, which makes it harder for a needle to pass through and harder to get flat under quilting. It is done, and many quilters regret it.

What seam allowance for a quilt backing? Half an inch, not the quarter inch you use everywhere else. A wider seam allowance lies flatter on a seam this long, which is the one thing a backing has to do.

Should I press the backing seam open or to the side? Open lies flatter, and the quilting will cross that seam many times and secure it. To the side is stronger on its own. For a quilt going to a longarm, press open.

Do I have to remove the selvage? Yes. It is a denser weave under different tension, so a seam that includes it behaves differently from every other seam in the quilt. And on a light backing the printed part shows through.

Why is my backing not the same size on both sides? Because the cuts were not identical, or the pieces shifted while you sewed, or the fabric was not cut straight at the shop. All normal. Fold it so the seam is parallel to the edge and trim.

Is wide backing worth the money? For anything twin sized or larger, look at the yardage. A queen backing is about eight and a quarter yards of 42 inch fabric or about three and a quarter yards of 108 inch. Less than half the fabric, and no seam.

Can I piece a backing from scraps? Yes, and it is a good use for them. It has to lie flat, it makes custom quilting harder, and many longarm quilters will not accept one. Ask before you build it.

Which way should the seam run? Whichever uses less fabric, unless the print has a direction, a nap, or your longarm quilter has a preference. Work the yardage both ways before buying, because the difference on a large quilt can be two yards.

Where this fits with the rest of the quilt

The backing is one of three layers, and the other two have their own decisions. Borders, backing, batting and binding covers the sequence from finished top to finished quilt, and how to make a quilt is the wider walkthrough if this is your first one.

If you would rather not make a sandwich at all, quilt as you go builds the backing into the process block by block, which sidesteps most of this page.

There are two shorter pieces on this site worth a minute each: a beginner walkthrough of piecing a backing, and a scale up rule for sizing one that gets you to a number without a table.

And when the quilting is done, binding in six steps finishes the edge.

Marbelia

P.S. The reason this task gets put off, I think, is that it sits in the gap between two pleasures. The piecing is over and the quilting has not started, and the backing is neither. But it is one seam. Cut it on a Tuesday evening with something on in the background and it is done before you have decided whether you like the program.