Batting extends beyond every edge
Add the chosen overage twice to width and twice to length. Four inches per side turns a 60 × 80 inch top into a 68 × 88 inch batting requirement.
Overage varies by setup
The 4-inch default is longarm-oriented and editable. Domestic-machine basting, longarm frames, and individual providers may require different margins.
Check roll orientation
A roll must cover one complete batting dimension without piecing. Use the quilt batting calculator to compare allowed orientations, or check backing overage.