A Free Calculator · Your Quilt, Your Fabric · Updated 2026
How much backing fabric does your quilt actually need?
Backing yardage is not a fixed number — it depends on your quilt top dimensions,
the overhang your longarm quilter or basting setup requires, and whether your fabric
is wide enough to cover the backing in one piece or needs a seam. Enter your numbers
and the calculator tells you the backing size, how many widths to cut and seam,
the exact yardage, and what to ask for at the cutting counter.
Backing dimensions with overhang·Widths to seam·Yardage rounded up to buy
Read this first
This calculator assumes standard 42″ quilting cotton and a horizontal seam when two
widths are needed. Enter your actual usable WOF after washing and trimming selvedges —
it's often 40–42″ even when the bolt label says 44″. If you're using 108″ wide
backing fabric, type 108 in the WOF field and the seaming step may disappear entirely.
Directional prints may need extra length to match the repeat across the seam;
this calculator does not add for that.
These are approximate finished quilt top dimensions commonly used as starting points.
Your actual quilt top may differ depending on block size, sashing, borders, and
personal preference — always measure your own top before calculating backing.
Size name
Approx. top dimensions
Backing needed (4 in overhang, 42 in WOF)
Widths to seam
Approx. yardage to buy
Crib
~36 × 52 in
44 × 60 in
2
~3.5 yd
Throw
~50 × 65 in
58 × 73 in
2
~4.25 yd
Twin
~60 × 80 in
68 × 88 in
2
~5 yd
Queen
~90 × 108 in
98 × 116 in
3
~10 yd
King
~108 × 108 in
116 × 116 in
3
~10 yd
All dimensions are approximate. Quilt top size varies by pattern, block count, and
border width. Backing and yardage figures in this table assume 4″ overhang per side
and 42″ usable WOF; queen and king assume 3 widths. Use the calculator above with
your actual top measurements for a precise result.
Why the overhang and seaming choices matter
Two decisions — how much overhang to leave and whether to use standard or wide
backing fabric — can mean the difference between a backing that loads cleanly
and one that comes up short on the frame.
The overhang is for the machine and the basting frame, not just aesthetics
A longarm quilting machine loads the quilt sandwich onto a set of rollers and leaders. The backing needs to extend far enough past the quilt top edges that it can be pinned or clamped to the leaders without any part of the quilt top going unsupported. Four inches per side is the standard minimum most longarm quilters specify — some ask for more. If you plan to hand-baste or spray-baste at home, you can work with less, but the margin shrinks fast when fabric shifts during layering. Cutting short here is how backings end up frustratingly close to the edge once the quilt is done.
108-inch wide backing eliminates the seam entirely for most quilts
Standard 42″ quilting cotton requires a seam for any quilt wider than about 34″ (after overhang). Wide backing fabric — 108″ wide, sold as "quilt backing" yardage — covers even a queen-size quilt in a single unbroken length, which is faster to prepare and removes any risk of a seam distorting during quilting. The trade-off: wide backing costs more per yard and you buy the full 108″ width regardless of how much you use. Type 108 into the WOF field above to see whether one length covers your specific quilt.
The seam placement is a choice you make after the yardage is set
Once you know you need two widths, you can place the joining seam wherever you prefer. The textbook approach — one full-width center panel with two half-width strips on either side — keeps the seam away from the quilt center where it is most visible. This uses exactly the same total yardage as a single center seam; it's a cutting decision, not a buying decision. The calculator gives you the yardage you need; how you arrange the pieces to avoid a center seam is up to you.
How to prepare the backing once you have the fabric
Buying the right yardage is step one. Getting the backing square, pressed, and
seam-free enough for quilting takes a few more steps.
Pre-wash the fabric before you cut
Quilting cotton shrinks — typically 2–4% in both directions. If you pre-wash the backing but not the top (or vice versa), the sandwich will pucker the first time the finished quilt goes in the wash. Wash and dry the backing fabric on the same settings you plan to use for the finished quilt before you cut or seam anything.
Trim the selvedges before measuring your WOF
The tightly woven selvedge edge does not behave like the rest of the fabric — it can pucker a seam or cause distortion under the longarm. Trim both selvedges off (usually ½–1 inch per side) before you measure the usable width and before you cut your lengths. This is why the usable WOF is often 40–41″ even when the bolt says 44″.
Press the seam open or to one side — consistently
A seam that alternates direction creates ridges visible from the front of the finished quilt and can cause the longarm to skip stitches where the thickness changes abruptly. Press the joining seam fully open or fully to one side (both are acceptable; pick one and commit) and press the whole backing flat before layering the sandwich.
Square up the backing before loading
A backing that is not square — or that has a diagonal pull from a seam that was sewn off-grain — will cause the quilted sandwich to distort. After pressing, fold the backing in half along the length and check that the fold is straight and the edges align before loading onto the longarm or spreading for basting.
Leave the overhang until after quilting
Do not trim the backing down to the quilt top size before quilting — that defeats the purpose of the overhang. The backing is trimmed flush with the quilt top edge after quilting is complete and before binding is attached. Trimming before quilting removes the insurance margin that keeps the corners square through the longarm process.
Where to buy
Got your numbers? Here's where to pick up what you need:
The terms that show up in patterns, on fabric bolts, and in longarm quilter intake
forms — briefly defined.
Width of fabric (WOF)
The usable width of a fabric after washing and trimming selvedges. Standard quilting cotton is labeled 44″ but yields a usable WOF of 40–42″ after prep. Always measure your actual cut fabric rather than trusting the bolt label — the difference between 42″ and 40″ can shift a two-width quilt into needing three.
Backing length vs. backing width
The backing length runs parallel to the quilt's long dimension and is the measurement you multiply by the number of widths to find total yardage. The backing width determines whether you need one or two (or three) widths. Confusing the two is one of the most common backing calculation errors.
Selvedge
The tightly woven finished edge that runs along both sides of the fabric as it comes off the loom. Selvedges are firmer than the body of the fabric and behave differently under a needle. They should be trimmed off before seaming a backing — leaving them in causes puckered, uneven seams.
Overhang (float)
The extra backing fabric that extends beyond the quilt top on all four sides. The overhang exists so the backing can be secured to the longarm leader, pinned to a basting frame, or held flat during hand-basting. Standard minimum is 4″ per side for longarm work; the overhang is trimmed flush after quilting, before binding.
Longarm quilting
Machine quilting performed on a dedicated frame where the quilt top, batting, and backing are loaded onto rollers and the machine head travels across the surface on rails. Longarm quilters specify minimum backing overhang because the frame needs fabric to clamp and tension. Many longarm quilters will refuse or recut a backing that arrives too small.
Wide backing fabric
Fabric woven to 108″ wide, marketed specifically for quilt backs. A single length covers most queen-size quilts without any seaming. It costs more per yard than standard quilting cotton and requires its own yardage calculation (type 108 in the WOF field above). Available in quilting cottons, polyesters, and blended fabrics.
Batting
The insulating middle layer of the quilt sandwich, between the quilt top and the backing. Batting is sized like the backing — it should extend at least 2–4″ beyond the quilt top on all sides. Pre-packaged batting (crib, throw, twin, queen, king) has specific package dimensions; check them against your backing size before buying.
Quilt sandwich
The three-layer assembly of quilt top, batting, and backing, held together for quilting. The backing must be larger than the batting, which must be larger than the quilt top — all three layers extend to different edges at this stage. After quilting, all layers are trimmed flush to the quilt top before binding is attached.
Frequently asked
The standard recommendation is at least 4 inches of overhang on every side — 8 inches total added to each dimension — when sending a quilt to a longarm quilter. That extra fabric gives the longarm machine something to grip and load onto the frame. If you're basting at home, 2–3 inches per side can work, but 4 inches is the safer number because it leaves room for shifting during basting. This calculator defaults to 4 inches per side and lets you adjust it.
Most quilting cotton is 42–44 inches wide off the bolt. Once you wash, press, and trim the selvedges, the usable WOF is typically closer to 40–42 inches. Many quilt tops — throws, twins, queens, kings — are wider than that after adding overhang allowance, so one length of fabric isn't wide enough. The solution is to cut two lengths and seam them side by side until the pieced backing exceeds the required width. This calculator handles the standard two-length horizontal seam scenario.
Wide backing fabric — sold as 108-inch or "quilt back" fabric — is woven specifically for quilt backs. It's wide enough to back a queen-size quilt as a single piece with no seams, saving time and eliminating the risk of a seam distorting during quilting. The trade-off: it costs more per yard. If you enter 108 as your WOF in the calculator above, it will show whether one length is sufficient for your quilt. Wide backing is popular among longarm quilters and anyone whose seam would fall awkwardly near the center of the quilt.
When you need two widths of fabric, cut one full length, then cut a second length in half lengthwise. Sew one half-width to each long side of the full-width center panel — the seams land near the edges rather than down the middle. This "split-width" construction is cosmetically cleaner and keeps seam allowances away from the quilt's center. The yardage is identical to a center-seam backing; it's a cutting arrangement, not a buying decision.
Fabric stores sell yardage in quarter-yard increments. You can ask for 4.89 yards but you'll be cut 5 yards — or occasionally 4.75, which would leave you short. Rounding up to the nearest quarter yard ensures you buy a cleanly cuttable amount that covers the requirement. The calculator shows both the precise yardage (what the math requires) and the rounded-up amount (what to request at the cutting counter).
The yardage this calculator produces is the total length of fabric to buy, accounting for the fact that two lengths are cut and laid side by side. It does not add extra for the joining seam allowance — a half-inch seam on each side uses about 1 inch from the width, not the length, so it doesn't affect how many yards you purchase. Where extra length does matter: directional prints may require matching the repeat across the seam. This calculator assumes a non-directional fabric.
Batting sizing follows the same logic as backing: extend at least 2–4 inches beyond the quilt top on all sides. Your batting dimensions should match or slightly exceed the backing dimensions this calculator gives you. Pre-packaged batting is sold in named sizes (crib, throw, twin, full, queen, king) with specific package dimensions — check the package against your backing size to confirm coverage before you buy.
Not always. If your backing width — quilt top width plus overhang on both sides — is at or under your usable WOF, a single length covers the full backing without seaming. This is common for crib quilts, wall hangings, and narrow lap sizes. The calculator handles this automatically: when the required backing width is at or under the WOF you enter, it reports one width needed and calculates yardage from a single length.
Common mistakes with this calculator
Backing yardage errors surface at the worst possible moment — when the quilt is loaded on
the longarm. These are the inputs most likely to produce a backing that comes up short.
Entering bolt width instead of post-wash usable WOF
A 44-inch bolt yields roughly 40–42 inches of usable fabric after washing, drying, and trimming selvages. Entering 44 instead of 42 can flip a two-width calculation into a one-width result — producing a backing that is 2–4 inches too narrow once the fabric is actually cut. Measure your washed and pressed fabric, trim the selvages, and enter that real number.
Calculating from the pattern size instead of the actual quilt top
Pattern dimensions and finished quilt top dimensions are rarely identical. Fabric stretches, seam allowances vary, and borders add differently than a schematic suggests. Measure your actual quilt top before buying backing. A difference of even 2 inches per side — well within normal variation — means 4 extra inches of backing width that the pattern size never predicted.
Using too little overhang for a longarm quilter
Most longarm quilters require at least 4 inches of backing overhang on every side so the machine's leaders have material to grip; some require 6 inches. Setting the overhang to 2 inches because it seems like enough can produce a backing your quilter cannot load. Check your quilter's requirements before buying — 4 inches per side is a safe default only if you have no other information.
Using a directional print without accounting for the joining seam
This calculator assumes non-directional fabric. If your backing uses a large-scale directional print, aligning the repeat across the horizontal joining seam requires extra length — typically one full pattern repeat per seam. Buying only the calculated minimum and then discovering the print doesn't line up means a return trip for more fabric, and likely a different dye lot.