textiles · tools

Rag Quilt Calculator

Plan a rag quilt: finished block math, blocks across and down, fabric shares by percentage, and yardage rounded to your chosen fraction.

Inputs

Finished quilt width (in)

Finished quilt height (in)

Top/Backing CUT square size (in)

Seam allowance / fringe depth (in)

Usable fabric width (WOF) (in)

Round yardage up to nearest (yards)

Set how the top is distributed by percentage. Shares should sum to 100% (give or take a percent).

Fabric	Share %	Blocks
Total	0%	0

If you use a single backing, set it to 100%.

Fabric	Share %	Blocks
Total	0%	0

Use a middle layer (batting/flannel)

Middle layer type

Middle layer CUT size (in) — leave blank for auto

Middle layer usable width (in)

Finished block size	–
Blocks across × down	–
Total blocks	–
Approx finished width × height	–

Fabric	Blocks	Squares / yard	Yards

How the math works

Finished block = cut size − 2× seam allowance.
Grid = ceil(quilt width ÷ finished block) × ceil(quilt height ÷ finished block).
Squares per yard = floor(usable width ÷ cut size) × floor(36 ÷ cut size).
Yardage per fabric = roundUp( blocks ÷ squaresPerYard, to nearest chosen fraction ).
Middle layer auto-cut = top cut size − 2× seam allowance (keeps it out of seams).

Real life adds plot twists: prewash, shrinkage, directional prints, plaids, and fussy cutting. Add a safety buffer.