How many granny squares do you need for a blanket?

How many squares you need

Take the width you want, subtract the border on both sides, and divide by the size of one square. Do the same for the length. For a 50 × 60 inch throw with 6 inch squares and a 2 inch border:

• Across: (50 − 4) ÷ 6 = 7.7, so 8 squares.
• Down: (60 − 4) ÷ 6 = 9.3, so 9 squares.
• That is 72 squares, and the blanket finishes at 8 × 6 + 4 = 52 inches by 9 × 6 + 4 = 58 inches.

Whole squares rarely land on the exact size, so decide whether you'd rather be as close as possible, at least that big, or no bigger. Open the Granny Square Blanket Calculator and it does the sums, including the joins.

Joins change the size

Each seam between squares adds a little width. Join-as-you-go adds nothing, because the squares are joined in their last round. A slip stitch seam adds about 1/8 inch, a single crochet seam about 1/4 inch, and a flat braid join about 1/2 inch.

That adds up: with slip stitch seams, the throw above has 7 seams across and 8 down, so it finishes at about 52⅞ × 59 inches instead of 52 × 58. Choose your joining method before you plan the layout.

Measure a square properly

Make a square, block it, then measure it. Blocking means pinning the square to its finished size on a foam mat, misting or steaming it and letting it dry. Unblocked squares curl and pull, and can be half an inch smaller than they will end up. Squares made with the same hook over a few weeks are usually closest in size.

How much yarn a granny square uses

A classic 6 inch granny square in worsted weight uses about 20 yards (18 m). The 72-square throw needs:

For your own tension, weigh one finished square and enter its weight in One square weighs. The calculator turns grams into length using your skein's label.

Yarn for each colour

Each round of a granny square is bigger than the one before, so later rounds use much more yarn. In a square of 4 rounds, round 1 uses 1/16 of the yarn, round 2 uses 3/16, round 3 uses 5/16 and round 4 uses 7/16. In general, round n of r uses (2n − 1) ÷ r².

With three colours for the first three rounds, and the last round, joins and border in a main colour, the throw needs about:

• Colour A (round 1): 98 yards, 1 skein
• Colour B (round 2): 294 yards, 2 skeins
• Colour C (round 3): 490 yards, 3 skeins
• Main colour (round 4, joins and border): 1,013 yards, 6 skeins

That's with 200-yard skeins and 10% extra. Buying the same number of skeins for every colour would leave you with far too much of the centre colour and not enough of the main one.

Plan a blanket, step by step

1. Choose a Blanket size, or enter your own Width and Length.
2. Enter your Square size, Joining method and Border width.
3. Pick Round to: the nearest size, at least your size, or no bigger than it.
4. Set Rounds per square and Colours rotated, and tick whether the last round, joins and border use a main colour.
5. Check the yarn weight and your skein's length and weight, then read the layout, the yarn for each colour and the preview.

Already made a pile of squares?

Switch to Squares I have and enter how many you've made. The calculator finds the layout closest to your blanket's shape that leaves the fewest squares over: 60 squares make a 7 × 8 blanket with 4 to spare, and it tells you how many more would make another row.