Taller by Fall

Baby clothes sizes, 0 to 24 months

Baby sizes are named in months, but the month on the label is about when an average baby outgrows it, not when it starts to fit. A 6M is for a baby from about 3 months up to 6.

Baby size chart

Size	Length (in)	Weight (lb)	Outgrown at (months)
Newborn	up to 21.5	6 to 9	1
3M	21.5 to 24	9 to 12.5	3 to 4
6M	24 to 27	12.5 to 17	7 to 8
9M	27 to 28.5	17 to 21	9 to 11
12M	28.5 to 30	21 to 25	12 to 14
18M	30 to 32	25 to 28	17 to 19
24M	32 to 34	28 to 30	22 to 24

Sizes from Carter's size chart. Gap, Old Navy and The Children's Place are within about an inch. The last column is the age when a baby of median length passes the top of the size, from the WHO growth standards. Boys reach it a little sooner than girls.

Half of all babies are longer than average, and they outgrow each size sooner than this. Go by length and weight, not by age. When the two point to different sizes, buy the bigger one.

Reading the labels

A single number means "up to". 6M fits until about 6 months.
A range means the same thing. 3-6M is the same size as 6M, and 6-12M covers both 9M and 12M.
Newborn size lasts about a month for an average baby. Buy very little of it.
24 months and 2T are different sizes. See 24 months vs 2T.

What to buy for next year

Babies grow about 10 inches in the first year and about 5 in the second. That is five clothing sizes in year one and two more in year two, so buying a year ahead means jumping several sizes at once.

This table is for a baby of average length. It shows the size to buy at a clearance today so that it fits through the same season next year.

Baby's age today	Wears now	Buy for next year
Newborn	Newborn	18M
3 months	6M	24M
6 months	6M	24M
9 months	9M	2T
12 months	12M	2T
18 months	24M	3T

With babies, the season matters as much as the size. A snowsuit only helps if the size it will fit lines up with the months it is cold. Work out how old your baby will be when the weather comes back, and buy for that age.

What is safe to buy ahead

Good bets: coats, snowsuits, swimwear and holiday pajamas in the size from the table. Those are the seasonal things that go on clearance.
Leave for later: anything fitted, and shoes. A baby who is not walking yet does not need them, and you cannot guess the size.
Keep the tags on. In the first months a baby can grow an inch in a month, which is most of a size.

From age 2 the calculator can do this for your kid's own height.

Open the size calculator

Where to look

Amazon Target Walmart

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One short email when each season's markdowns begin: coats in January, swimsuits in July, costumes on November 1. Nothing else.

More guides

Clearance