Granny square colour planner

Arranging squares so matching colours never touch is fiddly by hand, and the outer rounds of a square use far more yarn than the centre. This planner makes a layout with no matching neighbours, shows it as a coloured grid, and works out the yarn for each round and each colour, including a shared colour for the last rounds.

How to use the planner

1. Enter the squares across and down, the rounds in each square and the yarn one square uses.
2. Enter how many final rounds share one colour, such as a cream outer round (0 if each square is one colour).
3. List your colours and name the shared colour.
4. Choose whether matching colours may touch at the corners. Change the layout number for a different arrangement.

How the planner works

Each round of a solid square adds a ring around the last one. Round r adds an area of r² − (r − 1)², so out of R rounds it uses:

Share of round r = (2r − 1) ÷ R²

In a 5-round square the rounds use 4%, 12%, 20%, 28% and 36% of the yarn. The colour of each square's centre rounds gets its own share; the shared colour gets the last rounds of every square.

The layout is found by trying colours square by square and going back a step whenever a colour would touch its match. It always tries the least-used colour first, so the counts stay even. The same layout number always gives the same layout.

Reading your results

• Squares and the last round's share of the yarn.
• Yarn each round uses: the share and length of every round in one square.
• Yarn per colour: squares, yarn and balls for each colour, and for the shared colour.
• Layout: a grid of the centre colours, with letter codes to follow as you join.

Worked example

A 10 × 10 blanket of 5-round squares, 25 yd each, with the last round of every square in cream.

• Round 1 uses 1 yd of each square and round 5 uses 9 yd (36%).
• The centre colours share the first 4 rounds, 64% of each square: 16 yd per square.
• Cream needs 100 × 9 = 900 yd before any extra; with six colours, each one has 16 or 17 squares (256 or 272 yd).

Accuracy and limits

• The arithmetic is exact and covered by our automated tests. The shares assume solid rounds; open granny clusters grow a little more evenly, so the outer rounds come out slightly generous.
• Four squares meet at every corner, so keeping colours apart at the corners needs at least 4 colours; with fewer, the planner keeps them apart side by side only.
• Add about 10% to each colour for tails and joining.
• Very large grids, over 1,600 squares, are not supported.

Common mistakes

1. Buying the same yarn for every round. The outer round uses many times the yarn of the centre: buy more of the edging colour.
2. Losing the layout while joining. Label the squares by row and column before you start.
3. Too few colours. With two or three colours, some matching squares will meet at the corners.

Tips for more accurate results

• Weigh one finished square to get the yarn per square.
• Stack the squares in column order with a label on each pile, join each column into a strip, then join the strips.
• Then work out how many squares fit your size with the granny square blanket calculator.

Frequently asked questions