Quick answer. There is no standard size for a crochet baby blanket, whatever the roundups say. Of 54 free baby blanket patterns I went through, 12 never state a finished size at all, and among the 42 that do, only 2 land on the supposed 30 by 40 inch standard. The real spread runs from 18 by 28 inches to 43.5 by 50.75, a factor of 4.4 in area, with a median around 33.5 by 40. Pick the size from how the blanket will be used, then work the yarn out from the area.
The size complaint on baby blankets is the loudest one in crochet, and it is entirely predictable. Someone follows a pattern to the letter, finishes it, and it turns out to be a lap blanket when they wanted something for the cot, or a bedspread when they wanted something for the car seat.
So I counted. 54 free crochet baby blanket patterns from published roundups, recording the finished size each one states.
Nearly a quarter of patterns never say what size it will be
12 of the 54 give no finished dimensions anywhere. Not in the materials list, not in the notes, not at the end. You are told a hook, a yarn, and a starting chain, and the size is whatever that chain happens to produce at your tension.
That is the single most common way a baby blanket comes out wrong, and it has nothing to do with skill. If the pattern does not state a size, your gauge being slightly off the designer’s compounds across two hundred stitches with nothing to check it against.
The 30 by 40 inch standard is not standard. Exactly 2 of the 42 patterns that state a size come out at 30 by 40 give or take an inch. It gets repeated everywhere because it is the size of a cot blanket in a sizing chart, not because it is what people write patterns for. Nearly everything published is something else.
What 42 patterns actually come out at
| Finished area | Roughly | Patterns |
|---|---|---|
| Under 900 sq in | up to about 28 x 32 in | 6 |
| 900 to 1,600 sq in | about 30 x 30 to 40 x 40 | 29 |
| Over 1,600 sq in | 40 x 40 and up | 7 |
The smallest in the set is 18 by 28 inches, which is a pram or car seat cover. The largest is 43.5 by 50.75, which is a proper toddler blanket that will still be in use at four years old. The median is 1,307 square inches, or roughly 36 inches square.
15 of the 42 are square, which is a third of everything published. A square baby blanket is not a compromise, it is a deliberate choice: it works for a floor mat, a swaddle and a pram, and it has no wrong way round.
Size by what it is for, not by age
Age charts are the wrong tool because a newborn blanket and a cot blanket are different objects, not different sizes of the same object.
Pram, car seat, capsule: 18 by 28 to 30 by 30 inches. Small enough not to trail on the ground or tangle in straps. This is the one most often given as a gift and most often made too big.
Lovey or comfort blanket: 12 to 18 inches square. Meant to be gripped and carried, and small enough to be finished in a couple of evenings.
Floor and tummy time: 36 inches square upward. Needs to be square, needs to be washable, and this is where a dense stitch pays for itself because it stays put on a hard floor.
Cot or crib: around 30 by 40 to 36 by 45 inches. Bigger than this and it hangs over the sides, which is both untidy and, on a cot in use, not what you want.
Toddler bed: 40 by 50 upward. Make it the size they will grow into, since this is the one that gets kept.
Getting the size and the yarn right before you start
1. Decide the use, then the two dimensions in inches
Write both down. This is the only decision that cannot be revised at row forty.
2. Check whether your chosen pattern states a finished size
If it does not, treat the chain count in it as a suggestion rather than an instruction, and work out your own from your gauge.
3. Swatch and get your stitches per inch
Six inches wide, measured across the middle. Multiply your target width by that number, adjust up to the pattern repeat, and that is your chain.
4. Multiply width by length for the area
A 36 by 40 inch blanket is 1,440 square inches. Keep this number, because it is what tells you the yarn.
5. Multiply the area by yards per square inch
Open, cluster stitches like granny run around 0.9 to 1.0 yards per square inch in worsted weight; dense textured stitches run 1.25 to 1.4. So that 1,440 inch blanket is roughly 1,300 yards in a granny stitch and 1,800 in a dense one. The yardage breakdown has the figures those come from.
6. Buy above the number, in one dye lot
Round up by a skein. Baby blankets are the projects most likely to be given to a deadline, and running short at the last two rows is how deadlines get missed.
Things the numbers do not cover
Safety is not a size question. A blanket in a cot with a sleeping baby is a separate decision from what size to crochet, and it belongs to whoever is looking after the child. Open, lacy stitches also raise a snagging question for small fingers that no measurement addresses.
Washability outranks size for anything used daily. A blanket that has to be hand washed will be used once. Check the yarn band before the pattern.
Square blankets need a different chain calculation. Row gauge and stitch gauge are not the same number, so a chain that gives 36 inches wide does not give 36 inches long at the same row count. Measure the length as you go rather than counting rows.
Gift blankets get used later than you think. If you are making it for a newborn, the bigger sizes get more months of use, and a pram size is outgrown by the time the thank you note is written.
For the fabric side of the decision, how wide each stitch runs on the same yarn has the measured width figures, and the border stitch count is worth reading before you edge it, because baby blankets are small enough that a ruffled border shows.
Questions people ask about baby blanket sizes
What is the standard size for a crochet baby blanket?
There is not one in practice. 30 by 40 inches is quoted everywhere, but only 2 of the 42 patterns I measured come out at that size. Published patterns cluster between 30 and 40 inches on each side, with a median around 33.5 by 40.
How much yarn does a baby blanket take?
Area in square inches multiplied by 0.9 to 1.4 yards, depending on how dense the stitch is. A 36 inch square works out between about 1,150 and 1,800 yards in worsted weight.
What size baby blanket for a car seat or pram?
Between 18 by 28 and 30 by 30 inches. It has to stay clear of the floor and clear of the harness, which rules out anything cot sized.
Should a baby blanket be square or rectangular?
Square is a third of all published patterns and it is the more flexible shape: floor mat, pram, swaddle. Rectangular suits a cot better because it matches the mattress.
Why did my baby blanket come out a different size to the pattern?
Either the pattern never stated a size, which is true of nearly a quarter of them, or your gauge differs from the designer’s. Measure your stitches per inch and compare it against the pattern’s gauge line to see which.
How do I make a baby blanket bigger or smaller?
Change the starting chain, keeping it to the stitch repeat, and work more or fewer rows. Do not change hook size to change size: that changes the fabric as well, and on a baby blanket a looser fabric means bigger holes.
