A little help with the quilt maths

01 · BACKING

A 60″ × 72″ quilt top

Start with 42″ of usable fabric width, a 4″ overhang on every side and a ½″ seam allowance on each joined edge. The required backing is 68″ × 80″: add 8″ to both quilt dimensions.

1. Seams along the length: cut two panels, each 42″ × 80″. Joining them consumes 1″ in total, giving an 83″ × 80″ backing before trimming. You need 160″ of fabric length, or 4.444… yards. Round up to 4½ yards.
2. Seams across the width: cut two panels, each 42″ × 68″. Turn them and join them across the quilt to make a 68″ × 83″ backing before trimming. You need 136″ of fabric length, or 3.777… yards. Round up to 3⅞ yards.

Buy 3⅞ yards for the smaller full-width-panel plan, if your fabric can run in either direction.

If the print must run along the quilt’s length, turn off “Compare both fabric orientations.” A directional print can make the smaller plan unsuitable. The calculator does not include print-repeat matching, shrinkage or extra fabric for squaring up.

Why seams matter

Two 42″ panels do not make an 84″ backing after sewing. With a ½″ allowance on each edge, their joined width is 83″. A backing that needs the full 84″ will require a different plan or wider fabric.

Buying in metres

The shorter plan uses 136″ × 2.54 = 345.44 cm, or 3.4544 m. With purchases rounded up to 0.1 m, that becomes 3.5 m. Metre and yard purchase totals are rounded separately, so they need not convert exactly.

02 · BINDING

Binding the same 60″ × 72″ quilt

Use 2½″-wide straight-grain strips cut across 42″ of usable fabric, with 12″ extra for corners and finishing.

1. The perimeter is 2 × (60 + 72) = 264″.
2. Add the finishing allowance: 264 + 12 = 276″.
3. Seven strips provide 7 × 42 = 294″ before joining. Six diagonal joins use 6 × 2½ = 15″, leaving 279″. Six strips would leave only 239½″, so seven are needed.
4. Cutting seven strips uses 7 × 2½ = 17½″ of fabric length. That is 0.486… yards, rounded up to ½ yard.

Buy ½ yard and cut seven strips, each 2½″ × 42″.

The strip width is the unfolded cutting width. This calculation covers straight-grain binding with diagonal joins, not bias or flange binding. Backing and binding are separate purchases, even when you choose the same fabric.

03 · BLOCK LAYOUT

Six columns, eight rows, one border

Arrange 8″ finished square blocks in six columns and eight rows. Add a 3″ finished border on all four sides, with no sashing.

• Blocks needed: 6 × 8 = 48 blocks.
• Finished width: (6 × 8″) + (2 × 3″) = 54″.
• Finished length: (8 × 8″) + (2 × 3″) = 70″.
• With a ¼″ piecing seam, each assembled block should measure 8½″ unfinished, including its outside seam allowances.

Your finished quilt is 54″ × 70″. Choose “Use this size for my quilt” to recalculate backing and binding.

Unfinished block size is not the cutting size of every patch inside a pieced block. Follow your pattern for internal pieces. This tool does not calculate border yardage, sashing or internal patchwork fabric.

Before buying or cutting

Measure your actual quilt top, exclude selvages from usable fabric width and confirm your quilter’s overhang requirements. Add the allowances needed for your fabric and technique. The diagrams explain panel orientation; they are not full-size cutting templates.