Mixed-size granny square layout planner

Blankets that mix small and large squares look effortless but need careful planning so everything fits with no gaps. This planner places the large squares on a grid, fills the rest with small ones, shows the layout, and tells you the exact blocked size of each square so the joins line up.

How to use the planner

1. Enter the grid size in small squares, the size of a small square and the width each join adds.
2. Enter how many 2 × 2, 3 × 3 and 4 × 4 squares you want.
3. Read the layout and the blocked sizes. Change the layout number for a different arrangement.

How the planner works

Every large square must cover a whole block of grid cells. The planner places the largest squares first, without overlaps, and counts the cells left for 1 × 1 squares:

Small squares = grid cells − 16 × (4 × 4 squares) − 9 × (3 × 3) − 4 × (2 × 2)

A large square has to span the joins inside it too, so an s × s square blocks to:

Blocked size = s × small square + (s − 1) × join

The finished blanket is worked out the same way across and down, before any border. If the squares add up but cannot all be placed, the planner says so and suggests using fewer large squares or a bigger grid.

Reading your results

• 1 × 1 squares to fill the gaps and squares in total.
• Finished size: before any border.
• Block each size to: how many of each size, and the blocked size each must reach.
• Layout: a grid where each number is the size of the square covering that cell.

Worked example

A 12 × 16 grid (192 cells) of 3 in small squares with ¼ in joins, using two 4 × 4, six 3 × 3 and fifteen 2 × 2 squares:

• The large squares cover 32 + 54 + 60 = 146 cells, so 46 small squares fill the gaps: 69 squares in all.
• Block the 2 × 2 squares to 2 × 3 + 0.25 = 6.25 in, the 3 × 3 to 9.5 in and the 4 × 4 to 12.75 in.
• The blanket comes out 38.75 × 51.75 in before any border.

Accuracy and limits

• The sizes are exact and covered by our automated tests. The layout is found by trial, so a very tight arrangement may be missed; try another layout number or a slightly bigger grid.
• Every large square must be a whole multiple of the small one.
• Area alone is not enough: two 3 × 3 squares cannot fit in a 4 × 5 grid even though their area is smaller.
• There is no yarn estimate. Weigh one square of each size, or use the granny square blanket calculator for a single size.

Common mistakes

1. Making a 2 × 2 square exactly twice the small size. It must also cover the join between the small squares it replaces: 6.25 in, not 6 in, in the example.
2. Blocking to different sizes. Block every square of a size to the same measurement before joining.
3. Using a different join. Measure the join you will actually use, and enter that width.

Tips for more accurate results

• Add extra rounds to large squares, or adjust their last round, until they block to the size shown.
• Plan the colours of the small squares with the granny square colour planner.

Frequently asked questions