Quilt calculator

How to plan a quilt here

1. Pick a bed size or type the width and length you want; the page fits whole blocks of your size to it, and you can change the blocks across and down yourself. The quilt size shown includes the borders.
2. Name your fabrics and give each a colour (or a photo of the fabric, kept on this device). Then colour the grid: tap blocks, choose a starting layout, or start from a photo.
3. Add sashing and borders, and choose which fabric binds and backs the quilt.
4. Read the cutting list. Each fabric shows what to cut, how many strips across the width of fabric, and the length to buy. Print the PDF and take it to the shop and the cutting mat.

The formulas

• Size. Top = blocks × block size + (blocks − 1) × sashing, each way. Each border adds twice its width. Example: 5 × 6 blocks of 12 in make a 60 × 72 in top; a 2.5 in border makes the quilt 65 × 77 in.
• Squares. Cut size = finished + 2 × seam allowance. Per strip = floor(WOF ÷ cut size). Strips = ceil(squares ÷ per strip). Fabric = strips × cut size. Example: 120 squares of 6 in finished are cut at 6½ in; 42 ÷ 6.5 = 6 per strip, so 20 strips, 130 in, bought as 3⅝ yd.
• Half-square triangles are made two at a time: a square of each fabric cut at finished + seam allowance × (2 + √2), rounded up to ⅛ in (0.1 cm), so 6 in finished is cut at 6⅞ in with ¼ in seams. Each pair of squares gives two triangle blocks, so squares = ceil(triangles ÷ 2).
• Sashing between blocks is cut (sashing + 2 seam allowances) wide and (block + 2 seam allowances) long; the rows between block rows are joined from width-of-fabric strips.
• Borders. Two sides as long as the quilt inside them plus seam allowances, then two ends as wide as the quilt with the side borders on. Strips (border + 2 seam allowances) wide = ceil(total length ÷ WOF), joined end to end.
• Binding. Strips = ceil((perimeter + allowance for corners and joins) ÷ WOF), at 2½ in (6.5 cm) wide by default for a double-fold binding. Example: 2 × (65 + 77) = 284 in, plus 10 in, is 294 in: 7 strips.
• Backing. The quilt plus 4 in (10 cm) on every side, for the longarm or the shifting of hand basting. n widths joined with seams of 2 seam allowances cover n × WOF − (n − 1) × 2 × seam allowance. Vertical seams need enough widths for the backing's width, each as long as the backing; horizontal seams need enough widths for its length, each as wide as the backing. The page works out both and uses the smaller. Example: 73 × 85 in needs 2 × 85 = 170 in with a vertical seam but 3 × 73 = 219 in horizontally, so vertical. Batting is cut to the backing size.
• Yardage is each fabric's total, plus any shrinkage allowance, rounded up to ⅛ yd (4.5 in), or to 0.1 m in centimetres. Nothing is added for cutting mistakes: buy a little more if you want a margin.

Bed-size presets

Finished quilt sizes, width × length, from Missouri Star Quilt Co.'s quilt size chart (fetched 2026-10-20). Other charts differ by a few inches; measure your mattress and add the drop you want if it matters.

What it cannot do

• Straight-line squares and half-square triangles only. No curved piecing (Drunkard's Path), no appliqué, no English paper piecing of hexagons and no foundation paper piecing. A block is one square or one half-square triangle; for a pieced block such as a nine-patch, make each patch a cell.
• It cannot know your fabric will shrink. Shrinkage is only the allowance you type; cotton often shrinks 2–5% in the first wash.
• Every total depends on the width of fabric you enter. If your fabric gives 40 in after the selvages are trimmed, set 40: fewer pieces fit per strip and some totals go up.
• Directional prints are not handled: it assumes any piece may be turned. One-way fabrics and fussy cutting need more.
• No layout for wide backing fabric is guessed: for 108 in backing, set the WOF to its usable width and the backing becomes one piece.

Questions

How much fabric do I need for a quilt backing?

The quilt plus about 4 in on every side, joined from widths of fabric. For a 65 × 77 in quilt that is 73 × 85 in. Two widths of 42 in fabric joined with a vertical seam cover 83.5 in, so two lengths of 85 in, 170 in, are enough: 4¾ yd once rounded up to ⅛ yd. Joining horizontally would need three widths of 73 in, 219 in, so the vertical seam is the one to choose.

How many binding strips do I need?

Add the four sides of the quilt and an allowance for the mitred corners and the joins (10 in here), then divide by the usable width of fabric and round up. A 65 × 77 in quilt has a perimeter of 284 in; 294 in divided by 42 in is 7 after rounding up, so cut seven 2½ in strips, 17½ in of fabric.

How many squares can I cut from a strip of fabric?

Divide the usable width of fabric by the cut size and round down. A 6 in finished square is cut at 6½ in with ¼ in seam allowances, and 42 ÷ 6.5 is 6.46, so six squares per strip. 120 squares take 20 strips, 130 in, which rounds up to 3⅝ yd.

Can I make a quilt pattern from a photo?

Yes. Add your fabrics with their colours, then choose a photo: each block takes the fabric whose colour is closest to that part of the photo, measured in the OKLab colour space, which follows how people see colour differences. The photo is read inside your browser and is not uploaded or saved. Every block stays editable afterwards. With few fabrics and big blocks the result is a bold, simplified picture; more fabrics and more blocks follow the photo more closely.