Granny square planner

How to plan a granny square blanket here

1. Name your colours (2 to 12) and set how many rounds each square has.
2. Choose colourways: Random draws each square's rounds by the rule shown, Fixed list lets you set every colourway yourself, and Same centre / border keeps the first and last rounds the same in every square. Each colourway gets a letter.
3. Set the size: squares across and down, or a target blanket size with your square size and join allowance.
4. Shuffle until you like it. Tap squares to swap them or lock the ones you want to keep; Shuffle works around the locks.
5. Weigh a test square and enter the skein band's grams and metres to get the yarn and skeins per colour.
6. Print the PDF, then tick squares off as you make them.

The rules and formulas

• The square. The classic granny square in the variant of Easy on the Tongue, “Two Free Patterns to Crochet a Granny Square”, Pattern #1 (fetched 2026-10-22): clusters of 3 double crochet, a chain-2 space at each corner and chain 1 between clusters along the sides, the starting chain 3 counting as the first stitch. That page writes in US terms and gives UK treble (tr) for US double crochet (dc). Round n has 4n clusters = 12n dc, 4 corner spaces and 4(n−1) chain-1 spaces. Round 1 has 12 dc, round 4 has 48, a 6-round square 252 in all.
• The layout. Squares are dealt as evenly as the grid allows (48 squares and 5 colourways: three get 10, two get 9; which ones is decided by the seed). Then each square, row by row, takes a colourway that does not match the square above it, the square to its left or any locked neighbour, preferring the colourway with most squares left, and the search steps back when it gets stuck. With the toggle on, matching centre colours count as a clash too. If the counts cannot be even and clash-free they are relaxed; if no clash-free layout exists (one or two colourways, or locks that force it) the page fills every square with the fewest clashes and says so.
• Randomness. A new seed comes from your browser's cryptographic random generator. The seed drives a small stated generator (mulberry32) with rejection sampling, so the same seed, colourways and locks give the same layout, and the layout is decided before the squares slide into place.
• Blanket size. Width = across × square + (across − 1) × join allowance + 2 × border width; the same for the length. Each border round is taken to add as much as one round of your square: square size ÷ (2 × rounds) per side. Example: 8 across × 10 down of 15 cm squares with 0.5 cm joins and no border is 123.5 × 154.5 cm (48.6 × 60.8 in).
• Yarn per colour. One square uses S metres: your weighed grams × skein metres ÷ skein grams (or the metres you measured). Its rounds share S by their double crochets, so in an R-round square round n takes S × n ÷ (R(R+1)/2). Chains are not counted separately. Worked example: a 4-round, 20 g square in 100 g / 200 m yarn is 40 m; its rounds take 4, 8, 12 and 16 m. Each colour's total adds up every round it fills in every square.
• Joining and border. One double crochet's worth of yarn is S ÷ (12 × R(R+1)/2). Each seam between two squares takes one side of the last round: 3R of those. Seams = down × (across − 1) + across × (down − 1). Border round k takes 2 × (across + down) × 3R + 12k of them: the whole edge, plus the corners growing as a granny round does.
• Skeins = metres × (1 + extra %) ÷ skein metres, rounded up. The 10% extra for swatching and mistakes is yours to change.

What it cannot do

• Classic granny squares only: no solid granny, sunburst, hexagon, circle-in-a-square or other motifs.
• One square size per blanket, every square with the same number of rounds.
• Blankets only: no cardigan, bag or sweater layouts.
• Yarn is an estimate from your own test square and the stitch counts, not from a yarn database; chains and tension changes are not counted separately, and the joining and border figures use the rules above, not your own measurement.
• Colours on screen are not dye lots. Buy each colour from one dye lot.
• Saved on this device only: the plan and your ticks live in this browser's storage until you press Clear; nothing is uploaded.

Questions

How many granny squares do I need for a blanket?

Squares across = (blanket width + join allowance) ÷ (square size + join allowance), rounded to the nearest whole square, and the same for the length. For a 100 × 130 cm blanket of 15 cm squares with 0.5 cm joins and no border: 100.5 ÷ 15.5 = 6.48, so 6 across, and 130.5 ÷ 15.5 = 8.42, so 8 down. That is 48 squares and a 92.5 × 123.5 cm blanket; 7 across would give 108 cm. Choose Target blanket size and the planner rounds to the nearest whole square, border included, and shows the size you will actually get.

How much yarn does a granny square blanket take?

Make one square and weigh it. A 4-round square that weighs 20 g in yarn of 200 m per 100 g uses 40 m. Round n of a classic square has 12n double crochets, so its 4 rounds take 4, 8, 12 and 16 m. Multiply by how many squares carry each colour in each round, add joining and border, and you have each colour's metres. Here that is done for every colour, with the skeins rounded up after a 10% margin you can change.

How do I stop the same colours touching?

Give each colour combination a letter and lay the squares so that no two sharing an edge have the same letter. Shuffle does that by search, keeping the counts as even as the grid allows; tick the centre option to keep matching centres apart too. With only two colourways the only clash-free layout is a checkerboard, and the page tells you so instead of pretending.

US or UK terms: dc or tr?

The granny cluster is three US double crochets (dc), which UK patterns call trebles (tr). It is the same stitch. Switch the terms and every round line changes.