Quilt Backing & Binding Calculator

Frequently Asked Questions

How much backing fabric do I need?

Add 4–8 in to each side of the quilt top for longarm handling, then figure how many widths-of-fabric (WOF) cover the length. A 70 × 90 in top with 4 in margin needs ~78 × 98 in of backing; from 42 in usable WOF that's 2 widths × 98 in ≈ 5.5 yds.

Lengthwise or crosswise seam?

A horizontal (crosswise) seam runs across the quilt and usually needs fewer yards but a more visible seam. A vertical (lengthwise) seam runs top-to-bottom and often costs more yardage but lies flatter on a bed. Pick whichever uses less fabric or hides best.

How much binding do I need?

Binding length = perimeter + about 12 in for mitered corners and join. A 70 × 90 in quilt has a 320 in perimeter, so plan ~332 in of binding. From 2-1/2 in strips on 42 in fabric, that's 332 ÷ 42 ≈ 8 strips, about 5/8 yd.

Should I pre-wash backing fabric?

Wash the backing if the quilt top was pre-washed, to prevent uneven shrinkage. If neither is washed, expect 2–4% shrinkage on the first wash, which creates the classic crinkled quilt look.

Provided by AllCalculators.io
Free online calculators for everyday. No registration required.

Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

JavaScript is required to use the interactive calculator above. The questions and answers below remain readable without JavaScript.

How This Calculator Works

A quilt has three layers, and the one that quietly ruins projects is the backing, because it is the largest single piece of fabric and the one most often bought short. The longarm or domestic quilting process requires the backing to be larger than the quilt top on every side - the standard rule is a 3 to 4 inch overhang per edge so the quilt can be loaded on a frame, basted, and squared without the top running off the edge. This calculator takes your finished top width and length, adds the overhang on all four sides, then works out how the backing has to be pieced from standard-width quilting cotton (typically 42–44 inches usable after selvedges). For anything wider than a single bolt it tells you whether to seam two panels horizontally or run several vertical panels, and gives the total backing yardage rounded to the next eighth. It then sizes the binding separately: the perimeter plus corner and join allowance, divided into width-of-fabric strips at your chosen cut width (2¼ or 2½ inches are the usual double-fold figures).

Formula / Method

Backing width = top width + 2×overhang; backing length = top length + 2×overhang. Usable fabric width = bolt width − 1 inch (about ½ inch lost at each selvedge). If usable width ≥ backing width, a single uncut length covers it (no seam). If the goods turned sideways still cover the backing length, two panels with one horizontal seam need 2×backing width of fabric. Otherwise panels = ceil(backing width ÷ usable width) vertical panels, each backing length long. Backing yards = total inches ÷ 36, rounded up to the next ⅛. Binding: perimeter = 2×(backing W + backing L); strips = ceil((perimeter + 10) ÷ usable width) to cover the join and mitred corners; binding yards = strips × cut width ÷ 36, rounded up. Any blank, zero, or negative entry skips the calculation so it never returns NaN.

Worked Example

A 60 × 80 inch top with a 4 inch overhang needs a backing 68 × 88 inches. From 44-inch goods the usable width is about 43 inches - less than 68, so you piece it. Two panels seamed horizontally would need each panel 68 inches wide, but the backing is 88 long, so vertical panels win: ceil(68 ÷ 43) = 2 panels, each 88 inches, totalling 176 inches ≈ 4.889 → 5 yards (rounded to the eighth, 4.875 then up). Binding: perimeter = 2×(68 + 88) = 312 inches; (312 + 10) ÷ 43 ≈ 7.5 → 8 strips at 2½ inches = 20 inches ≈ 0.625 yard. So order roughly 5 yards backing plus ⅝ yard for binding (a fat half-yard is the safe round number).

Common Mistakes

Cutting the backing the same size as the top - a longarmer will refuse it; you need the overhang on every side.

Forgetting selvedge loss; the full bolt width is not usable, so a "42-inch" backing does not fit a 42-inch bolt.

Running panels the wrong direction and buying far more fabric than a sideways seam would have needed.

Sizing binding from the quilt-top perimeter instead of the larger trimmed backing/quilt edge after squaring.

Ignoring the join and corner allowance, so the last binding strip is an inch too short to close the loop.

Tips & FAQ

How much overhang does a longarmer want? Most quote 3–4 inches per side; ask yours before cutting, as some frames need a full 4–6 inches. Vertical or horizontal seams? The calculator picks whichever uses less fabric, but a single horizontal seam across the back is often less visible and lies flatter than two vertical ones - press it open and you will rarely notice it. What binding cut width? 2¼ inch makes a snug double-fold binding; 2½ inch is more forgiving for hand finishing and is the common default. Should I use wide backing fabric? 108-inch "extra-wide" quilt backing eliminates seams entirely on most quilts - if you can find it in a coordinating colour it is worth the slightly higher per-yard price. Why add 10 inches to the binding? You lose length to the diagonal or straight join between strips and to turning each mitred corner; running short on the final corner is the single most common binding failure. Pre-wash the backing? If the top is unwashed, leave the backing unwashed too so all three layers shrink together for that soft, crinkled finish after the first wash.

Quilt Backing & Binding Calculator

Frequently Asked Questions

Related Sewing Calculators