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Quilt Backing & Batting Calculator
Calculate yardage and seam layouts for standard 42" and 108" wide quilt backing fabrics with mandatory 4-inch longarm margins.
Calculate Backing Cuts
Backing Fabric Yardage:
4.35 yards
Total Backing Dimensions (with overhang):
68 × 78 in
Vertical Seams Required:
1 seam (2 panels)
Quilter's Field Manual
Why Longarm Overhang Matters
- 4-Inch Margin Rule: Longarm quilters require at least 4 inches (10 cm) of backing and batting extending past the quilt top on all four sides to clamp into the machine frame.
- Wide Back Savings: 108-inch wide backs require zero piecing seams, saving substantial labor and bulk.
The Math Formula
• Backing Cut Size = (Top Width + 8") × (Top Length + 8")
• Panels Needed = Backing Width ÷ Usable Bolt Width
• Panels Needed = Backing Width ÷ Usable Bolt Width