Granny Square Calculator
Squares needed for a blanket, and the finished size.
Calculate how many granny squares a blanket needs from the target size and square size, with the finished dimensions after joining.
Squares needed
20
4 across × 5 down
The joining method is part of the arithmetic. A lattice join adding half an inch per seam puts two and a half inches across five squares, which is the difference between a lap blanket and a throw. Add any border on top of these figures rather than inside them.
How the Granny Square Calculator works
A squares blanket is a tiling problem, and the joining method is part of the arithmetic. Squares joined with a seam sit tight against each other; joined with a chain or a strip of contrast, each one occupies a little more than its own size — and across eight squares that adds several inches, which is the difference between a lap blanket and a throw.
Also known as: crochet square blanket calculator · blanket squares calculator
Tiling, plus the join
The square count is the target width divided by the square size, rounded up, times the same for the length. Twelve inch squares over a 48 by 60 blanket is four across and five down, so twenty squares.
The join is the part that gets left out. Squares seamed with a whipstitch sit edge to edge and add nothing; squares joined with a row of single crochet add roughly a quarter inch per seam, and a chain-space or lattice join half an inch or more.
Across a row that compounds. Five squares joined with a half inch lattice have four seams between them, adding two inches to the width — enough to turn a planned lap blanket into a throw.
A worked example
Twenty 12 inch squares in a four by five grid, whipstitched: 48 by 60 inches exactly. The same twenty squares joined with a half inch lattice measure 49.5 by 62 — three seams across and four down, at half an inch each.
If the target is a fixed size, work backwards: subtract the join allowance from the target first, then divide by the square size. Otherwise the blanket comes out consistently larger than planned.
Where the answer misleads
Squares are rarely the size they are supposed to be. Individual squares vary with tension across a long project, and a set made over several weeks can differ by half an inch between the first and the last. Blocking each square to a template before joining is the fix, and it is worth the time on anything with more than about a dozen.
A border is not included in these figures and should not be. Borders are usually two to four inches all round, which is four to eight inches on each dimension — add it after the square grid rather than trying to absorb it.
Finally, standard blanket sizes are conventions rather than rules: a baby blanket is around 30 by 36, a lap 36 by 48, a throw 50 by 60. Whether a blanket is the right size is decided by what it is for, not by the table.
Frequently asked questions
How many granny squares do I need for a blanket?
Divide the target width and length by the square size, round each up, and multiply. A 48 by 60 inch blanket from 12 inch squares is 4 across by 5 down, so 20 squares.
What size should the squares be?
Larger squares finish faster and need less joining; smaller ones use scraps better and are more portable. Six to twelve inches covers most projects, with 12 inch squares being the usual choice for a full blanket.
How much does joining add?
A whipstitch or slip stitch join adds almost nothing. A single crochet join adds roughly a quarter inch per seam, and a chain-space or lattice join can add half an inch or more — across a row of five squares that is two and a half inches.
What are standard blanket sizes?
A baby blanket is around 30 by 36 inches, a lap blanket 36 by 48, a throw 50 by 60, and a twin bed cover about 66 by 90. Add a border to those figures rather than including it in the square count.