Quilt Backing & Binding Calculator
Seam orientation is worth up to a yard, and it flips on most standard sizes. One inch of quilt can cost 2.4 yards of backing.
Which way you seam the backing is worth real fabric
Almost everyone seams a backing vertically without thinking about it — two long panels side by side. But the panels can run either way, and because the panel count is a ceiling, the two orientations can differ by a lot. Across the standard sizes, 5 of 7 come out cheaper seamed the other way.
| Quilt | Vertical seams | Horizontal seams | Better | Saves |
|---|---|---|---|---|
| Baby / crib 36×52″ | 2p · 3.33yd | 2p · 2.44yd | horizontal | 0.89yd |
| Lap 50×65″ | 2p · 4.06yd | 2p · 3.22yd | horizontal | 0.83yd |
| Throw 60×70″ | 2p · 4.33yd | 2p · 3.78yd | horizontal | 0.56yd |
| Twin 66×90″ | 2p · 5.44yd | 3p · 6.17yd | vertical | 0.72yd |
| Double / full 80×90″ | 3p · 8.17yd | 3p · 7.33yd | horizontal | 0.83yd |
| Queen 90×100″ | 3p · 9.00yd | 3p · 8.17yd | horizontal | 0.83yd |
| King 108×100″ | 3p · 9.00yd | 3p · 9.67yd | vertical | 0.67yd |
The saving reaches most of a yard, for a decision that costs no extra work and the same number of seams. Worth ten seconds before you buy.
One inch of quilt can cost two and a half yards
Backing yardage is a step function of the panel count, so the cost of making a quilt slightly bigger is wildly uneven. Between the steps, another inch is free. At a step it is brutal: going from 76″ to 77″ wide on a 90″ quilt adds 1.64 yards, because it tips the backing from two panels to three. At 119″ the same single inch adds 2.42 yards.
This is worth knowing while the design is still on paper. If you are near a step, losing an inch off the border — or gaining one — can be the difference between three panels and two, and nobody will ever notice the inch.
Binding does the same thing, more gently
Strips are cut across the fabric width, so the strip count is another ceiling — half an inch of quilt can cost a whole extra strip. It is a smaller step than the backing one, but it is the same shape of problem, and it is why binding yardage never looks proportional to quilt size.
Bias binding is a different calculation entirely. Cut on the diagonal, it comes out of an area rather than a row of strips, so the tool sizes a square instead of counting strips. You need bias for curved edges — it stretches around them where straight-grain binding will not — and it is noticeably hungrier. Straight grain is fine, and cheaper, for anything with square corners.
Notes
- Usable width is not the width on the bolt. Quilting cotton sold as 44″ gives about 42″ once the selvedges are off, and less if it shrank in a pre-wash. Measure a piece you already own rather than trusting the label.
- Four inches of overhang each side is the usual request. A longarm quilter needs it to load the quilt; check with yours, because some ask for more. If you are quilting it yourself on a domestic machine you can trim that back.
- Wide backing fabric changes everything. 108″ backing turns almost any quilt into a single seamless panel. Put the real width in the box and watch the panel count collapse to one.
- Press the backing seams open. A pressed-to-one-side seam makes a ridge that a longarm will find, and it is the one seam in the quilt nobody will ever unpick.
How to use
- Pick a quilt size or enter your own measurements.
- Set the overhang your longarm quilter asks for.
- Put in your real usable fabric width, not the number on the bolt.
- Seam the backing whichever way the tool says is cheaper.
Frequently asked questions
How much fabric do I need for a quilt backing?
Enough to cover the quilt plus an overhang on every side, made up of whole widths of fabric. Because the panel count rounds up, the answer is a step function rather than a smooth one — which is why it rarely looks proportional to the quilt size.
Should backing seams run vertically or horizontally?
Whichever needs less fabric, and it is genuinely worth checking — across the standard quilt sizes most come out cheaper seamed horizontally, saving up to most of a yard. Almost everyone defaults to vertical without comparing, and it costs no extra work or seams to do it the other way.
Why did adding an inch cost me yards of fabric?
Because you crossed a panel boundary. Going from 76 to 77 inches wide on a 90-inch quilt adds 1.64 yards, and at 119 inches a single inch adds 2.42, because each tips the backing into another whole width of fabric. Between the steps, extra inches are free.
How much overhang does the backing need?
Four inches on each side is the usual request, so the quilt can be loaded on a frame. Check with your longarm quilter, since some ask for more — and if you are quilting it yourself on a domestic machine you can trim that back.
What is the usable width of quilting cotton?
About 42 inches for fabric sold as 44, once the selvedges are trimmed off — and less again if it shrank in a pre-wash. Measure something you already own rather than trusting the label, because this figure decides the panel count and therefore the whole answer.
How many binding strips do I need?
The perimeter plus about ten inches for the corners and the join, divided by your usable fabric width and rounded up. It is a ceiling, so half an inch of quilt can cost a whole extra strip — the same quantisation as the backing, just gentler.
Do I need bias binding?
Only for curved edges, where it stretches around the curve and straight-grain binding will not. It is cut on the diagonal so it comes out of an area rather than a row of strips, which makes it noticeably hungrier. For anything with square corners, straight grain is fine and cheaper.
Does wide backing fabric help?
Enormously. 108-inch backing turns almost any quilt into a single seamless panel, which removes the seam, the pressing and the whole panel-step problem at once. Put the real width into the box and watch the panel count collapse to one.
Does this send anything anywhere?
No. Everything is calculated in your browser and nothing is stored or uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.