Quilt Calculator

Why a Backing "Close Enough" to the Top Fails at the Longarm

Making backing only as big as the quilt top, or with a token inch of overhang, then sending it to a longarm quilter who needs four inches on every side to mount it on the frame, is the error that causes the most grief. A backing even an inch short can mean the quilt cannot be loaded at all, forcing a second fabric order, sometimes in a dye lot that no longer matches. Always size backing and batting from the quilt top plus the full overhang, confirm the number your quilter requires, and cut once. The few extra inches of fabric cost far less than a second order and a returned quilt, and this calculator builds that margin in by default. The National Quilting Association provides backing and overhang preparation standards for longarm quilting that explain why the standard margins are sized as they are.

What the Quilt Calculator Actually Does

This tool works out the three fabrics every quilt needs, backing, batting, and binding, from the finished dimensions of a quilt top. Enter width and length, choose fabric width and overhang, and it returns backing yardage with the most efficient seam layout, batting cut size with a recommended stock package, and binding strip count and yardage. As the Crafty Quilter sizing guide stresses, getting backing and batting size right before cutting keeps the finished quilt square and saves an expensive trip back to the fabric shop. This calculator optimises the backing layout rather than just dividing area by width, since a pieced backing can run seams vertically or horizontally, and one direction usually wastes less fabric, computing both and recommending the cheaper one.

How Backing Yardage Is Calculated

Backing starts with the quilt top plus overhang on every side, the standard is four inches per side, adding eight inches to both width and length. If the backing width fits within one usable width of fabric, the bolt width minus trimmed selvages, one length of fabric is enough. Most bed-size quilts exceed a single 42-inch width, so backing must be pieced from two or three panels joined with seams. Running seams vertically divides backing width into fabric widths, while running them horizontally divides backing length instead, and the two layouts rarely need the same amount of fabric. As the Sew Nikki backing chart shows, the efficient choice depends on how the quilt's proportions divide into fabric width, and this calculator works out both and picks the one using less, which can save more than a yard on a large quilt. The same width-nesting logic powers our general Fabric Calculator for non-quilting projects.

Batting and Binding

Batting follows the same rule as backing, larger than the quilt top by the overhang on each side, so layers can shift during quilting and be trimmed square afterwards.

Binding wraps the entire edge, so its length is the perimeter, two times width plus two times length, plus about ten inches for joining strips diagonally and turning corners. Dividing by usable fabric width gives the number of strips to cut, multiplying strips by chosen strip width gives binding fabric needed. As the Quilting Wemple binding guide describes, strips are usually cut at 2.25 to 2.5 inches for a half-inch finished binding, the calculator's default.

Wide Backing Versus Piecing

One decision quietly determines how much fabric and time a quilt back costs: piecing standard fabric or buying wide backing. Standard quilting cotton is 42 to 44 inches wide, so any quilt wider than about 34 inches needs a pieced back. Wide backing, woven at 108 inches, is broad enough to back almost any quilt with no seam at all. The numbers can be striking, a queen quilt needing more than eight yards of pieced 44-inch fabric might need only a little over three yards of 108-inch wide backing, with no seam to sew or press. Wide backing costs more per yard, so the total price is closer than the yardage suggests, but the saved hours and seamless, flat back often tip the balance for bed-size quilts. This calculator surfaces the comparison automatically whenever standard-width fabric is selected, so the call can be made before buying.

Accuracy and Limitations

This calculator applies standard quilting formulas exactly: overhang added to each side, panels nested across usable width with both seam directions compared, perimeter-based binding, batting matched to stock package sizes. For a rectangular quilt with a simple pieced or whole-cloth back, the yardages returned are the amounts to buy, and the seam-direction optimisation reflects what an experienced quilter would work out by hand. It assumes a plain pieced backing without a deliberately patterned or fussy-cut back, which would need extra fabric for matching, and does not plan the quilt top's block layout itself. Usable width uses bolt width minus selvages, but actual usable width varies a little by manufacturer, so verify against your specific fabric when cutting fine. Directional prints on the backing may force a particular seam orientation regardless of which uses less fabric. The American Quilter's Society publishes the backing overhang conventions referenced in these calculations.