Two numbers decide whether a quilt survives its first wash: the loft of the batting, and the maximum distance the manufacturer allows between rows of quilting. Both are on the packaging, and both are routinely ignored.
Loft
Loft is thickness and spring. Low loft lies flat and shows off quilting stitches, which is why it is the usual choice for wall hangings, table runners and quilts that will be used hard. High loft gives the puffy, comforter-like quilt.
As a rough guide, cotton is low loft, wool sits in the middle with more spring than its thickness suggests, and polyester goes highest.
Stitch spacing
Every batting states a maximum distance between lines of quilting. Cotton typically needs stitching every two to eight inches, wool every three to four, polyester up to ten.
This is not a suggestion. Batting is held in place by the quilting, and if the gaps are too wide the fibers migrate and bunch the first time the quilt is washed. The quilt does not tear; it goes lumpy, permanently, and there is no fixing it.
Check the number before you plan the quilting design, not after.
How much to buy
Add at least four inches to each side of the finished quilt top — so eight inches to both the width and the length. That margin gives you something to hold onto while quilting and room to square up afterwards. If someone else is longarm quilting it for you, ask them: many want six inches per side.
Wool, briefly
Wool is the batting people fall for and then keep buying. It is warm without weight, springs back rather than creasing, and shows quilting stitches beautifully because of that spring. It costs more and it is worth trying once on a quilt you care about.
We list loft and maximum stitch spacing on every batting product, because those are the two things you actually need to know.