Quilt Backing & Batting
Backing and batting size from the quilt top and your overhang, and the fabric to buy: whole widths with seams along or across the quilt, whichever takes less.
The backing and batting dimensions, how many panels your fabric width needs and which way the seams should run for the least fabric, the yards or metres to buy, and the unused share.
Example: A 60 × 72 in top with 4 in overhang is a 68 × 80 in backing; on 42 in fabric with ½ in seams, two panels seamed across need 136 in = 3.78 yd, where seams along the length would need 4.44 yd.
Overhang, then
whole widths.
Why the backing is larger than the top, how panels are counted with their seams, why the seam direction changes the yardage, and what batting needs.
Overhang
A backing must be larger than the top on every side — for the quilting frame or machine to grip and for the layers to shift a little as they are quilted. The overhang is yours: a long-arm frame commonly wants more than a domestic machine, and the page assumes no figure. Backing width and length are the top plus twice the overhang.
Panels and seams
Fabric narrower than the backing is pieced from whole widths. With seams along the length, panels run the quilt’s length and the count comes from the backing width; with seams across, from the backing length. Each seam takes two seam allowances off the usable width, so the count is ⌈(span − 2s) ÷ (width − 2s)⌉. The fabric to buy is the panel count times the other dimension, and “least fabric” tries both directions and keeps the shorter cut — often the across-seam layout, which quilters sometimes overlook.
Batting
Batting is the top plus its own overhang on each side, usually smaller than the backing’s. Packaged batting sizes are the maker’s; the page gives the dimensions, and the pack you buy must cover them.
What the number does not settle
Directional prints and pattern matching across a backing seam, a pieced or decorative backing, and where exactly the seam falls (a centre seam can be avoided by splitting one panel) are layout choices; the page counts whole widths. Inputs stay in your browser; the same anonymous usage counts as the rest of the site apply.