Quilt Backing Calculator
Calculate yardage of quilt backing fabric required including the overhang needed for longarm quilting or stretching on a frame. Use it before purchasing backing to avoid trips back to the fabric store mid-project.
Last updated: May 2026
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About this calculator
The formula is: backingYardage = ((quiltLength + overhang × 2) × (quiltWidth + overhang × 2)) / fabricWidth / 36, where all dimensions are in inches, overhang is per-side fabric extending beyond the quilt top, and fabricWidth is the bolt width of the backing fabric. The × 2 reflects overhang on both opposing edges. Standard overhang: 4 inches per side for home machine quilting on a domestic machine; 8 inches per side for longarm quilting service (the longarmer needs to clamp and tension the backing); 4–6 inches per side for hand quilting on a frame. Quilters typically buy extra rather than less — running short of backing mid-quilt is painful. Bolt width considerations: most quilting cottons come in 42–44 inch widths; small quilts (baby, throw) fit on a single width; full-size and queen-size quilts need pieced backings (two or three widths joined with a vertical seam); king-size quilts need three widths. Wide quilt backings exist (108 inches wide) for king-size quilts to avoid piecing; these are sold by the yard and cost 30–50% more per yard than standard width but save the time and waste of piecing. Edge cases: zero overhang produces minimum-sized backing (risky); very large overhang produces wasteful estimates. Fabric direction also matters: if the backing has a directional print (one-way stars, scenes), the backing must be oriented for visual consistency, which may require extra fabric. Pieced backings should join in the center vertically (rather than horizontally) for a less visually obvious seam — the seam runs parallel to the quilt edges and gets lost in the quilting pattern.
How to use
Example 1 — Lap quilt for longarm quilting. Quilt top 60 × 80 inches; longarm overhang 8 inches per side; 44-inch quilting cotton backing fabric. Enter quiltLength 80, quiltWidth 60, backingOverhang 8, fabricWidth 44. Result: ((80 + 16) × (60 + 16)) / 44 / 36 = (96 × 76) / 44 / 36 = 7,296 / 1,584 ≈ 4.6 yards. ✓ Order 5 yards to allow for one cut error and the pieced-backing seam. For pieced backing: cut two pieces 96 inches long, join with a vertical seam (parallel to the quilt's long edge), and you have 80+ inches of pieced backing width — enough for the 76-inch needed with 4 inches extra. Example 2 — Small wallhanging on domestic machine. 36 × 48 inch wallhanging; 4-inch overhang for domestic quilting; 44-inch fabric. Enter 48, 36, 4, 44. Result: ((48 + 8) × (36 + 8)) / 44 / 36 = (56 × 44) / 44 / 36 = 2,464 / 1,584 ≈ 1.56 yards. ✓ Order 1.75 to 2 yards. Note that this quilt fits on a single width of 44-inch fabric (the 44-inch backing accommodates the 44-inch needed quilt-plus-overhang width); no piecing required. For a 50-inch-wide quilt, you would need to piece because 50 + 16 = 66 inches exceeds the single 44-inch bolt width.
Frequently asked questions
How much overhang do I need for quilting?
Depends on the quilting method. Hand quilting on a frame: 4–6 inches per side, enough to clamp into the frame edges with some margin. Domestic machine quilting (your own sewing machine): 2–4 inches per side; the quilt does not need to be heavily clamped. Longarm quilting service (where someone else quilts your top): 8 inches per side — longarm machines have specific bar widths and require sufficient backing to clamp and tension properly. Some longarmers may ask for 10 inches per side; ask your longarmer for their specific requirement before buying backing. If you are unsure: 6 inches per side is a safe default that works for most home methods and many longarmers; better to have slight excess than be short. The backing is trimmed flush after quilting (and before binding); excess overhang is simply wasted but the quilt is finished correctly. Buying too little backing means re-piecing or re-buying; always err generously.
When do I need to piece a backing vs use a single piece?
You need to piece when the quilt-plus-overhang dimensions exceed the bolt width of your backing fabric. Quilting cotton at 44 inches: maximum single-piece backing is about 38–40 inches wide (44 − 4 inches for seam allowance and trimming). So quilts narrower than ~38 inches can use single-piece backing. For wider quilts, you have three options: 1) Piece two widths together horizontally — most common; the seam is centered vertically. Two widths of 44-inch fabric give about 78 inches usable backing width — enough for full/queen quilts up to ~74 inches wide. 2) Piece three widths for king-size quilts — typically arranged as one full width centered and one half-width on each side, or three full widths. 3) Use a wide-back fabric (108 inches wide) sold specifically for this purpose; expensive but avoids piecing. The seam in pieced backing should be parallel to the long edge of the quilt (vertical seam in a portrait-oriented quilt) so the seam is less visually prominent and runs parallel to most quilting designs. Pre-wash backing fabric before assembling to handle shrinkage.
Should I pre-wash quilt backing fabric?
Yes, almost always — and for the same reason you pre-wash quilt top fabrics. Cottons shrink 3–10% in the first wash, and the backing must shrink at the same rate as the top to avoid puckering and distortion after the finished quilt is washed. If you do not pre-wash the top, do not pre-wash the backing; consistent treatment is more important than the choice itself. Many modern quilters do not pre-wash any fabrics, preferring the slightly crinkled "crinkle finish" that results when the finished quilt is first washed; the entire quilt shrinks together and looks intentionally crinkly. If you do pre-wash: wash the backing in warm water with a color-catcher sheet to absorb any bleeding dye; dry until slightly damp then iron flat. Some heavily dyed batiks and red cottons bleed strongly; test for bleeding by soaking a swatch in hot water with a color-catcher before deciding. Cotton/polyester blends shrink less than 100% cotton but rarely used for backing because the hand is wrong. For backing made of multiple fabrics (pieced backings using scraps), pre-wash each fabric separately first to handle differential shrinkage.
What are the most common backing mistakes?
The biggest is buying too little backing and discovering this mid-construction; the fabric store may be out of stock or have a different dye lot, ruining the project. Add 10–20% extra beyond the calculation. The second is not accounting for overhang correctly; longarm quilters specifically need 8 inches per side, and some quilters forget. The third is piecing the backing with the seam horizontal (parallel to the short edge) rather than vertical (parallel to the long edge); horizontal seams are more visually prominent and more likely to interfere with quilting designs. The fourth is using a different fiber content for backing than the top; cotton top with polyester backing creates differential shrinkage and the quilt warps. The fifth is using a fabric too lightweight for backing (lightweight quilting cotton or muslin) which lets the batting show through; use a quilting-weight fabric specifically intended for backing or a regular quilting cotton. The sixth is choosing a busy directional print as backing without realizing the prints must be oriented consistently across pieced sections; non-directional prints (small geometric, all-over botanical) are more forgiving. The seventh is leaving backing un-pressed before basting; wrinkles in the backing cause uneven tension during quilting. The eighth is not securing the basting layer adequately; safety pins should be placed every 4–6 inches across the entire quilt sandwich to prevent shifting.
When should I not use this calculator?
Skip it for very small quilts (potholders, mug rugs, mini-quilts under 18 inches) where backing is just a single small cut and yardage math is unnecessarily complex; buy 1/4 yard. It is the wrong tool for whole-cloth quilts where backing IS the top (single fabric layer plus batting plus a thin lining); the calculation differs. Do not use it for quilts that will be flipped (reversible quilts with two distinct sides); the "backing" becomes a second top and needs to be designed and yardage-calculated like a primary quilt top. For T-shirt quilts and memory quilts using non-traditional materials, the backing should be a stable woven that supports the often-stretchy or odd-weight T-shirt panels; use a heavier backing fabric and calculate at the higher fabric width if available. For art quilts and gallery quilts, sometimes the backing has integrated design elements (labels, embroidered signatures, contrast piecing) that require additional yardage beyond the simple overhang formula. And for wide-back fabric (108-inch bolt), the math is simpler — no piecing needed for most domestic quilts — and the calculator overstates required yardage if it assumes 44-inch bolts.