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What You Need to Know About Newborn & Baby Clothes Sizes

New parents are faced with a seemingly unending stream of decisions, purchases, and new routines well before their bundle of joy even arrives.

Near the top of parents’ to do checklist for new baby is buying clothes for the new baby.

Deciphering baby clothing sizes can be confusing, so in this article we’ll dig into how baby clothes sizes work and provide some baby clothes size charts to help clear things up.

How do baby clothes sizes work?

Clothes sizes for babies are typically labeled by age. Depending on the brand of clothing, some of the sizes you can expect to see are:

  • P (Preemie)
  • N (Newborn)
  • 0-3 months
  • 0-6 months
  • 3-6 months
  • 6-9 months
  • 9-12 months
  • 12-18 months
  • 18-24 months
  • 2T (2 years)
  • 3T (3 years)
  • 4T (4 years)
  • 5T (5 years)
  • 6T (6 years)

Each child is unique and grows at her own pace, so trying to buy clothes that fit and last more than a single wear can be a challenge.

Size differences between brands occur because brands design their baby clothes sizes by weight for each age group.

This means some clothes may fit your baby perfectly within their age range while others will be too large or too small.

The most important thing to note with respect to sizes is that they represent an average range, and the size listed will be the upper limit of that range. So, if you have a 3-month-old, they will likely be ready to graduate from 0-3 month sizes into 3-6 month sizes if they haven’t already. When in doubt, it’s best to size up. Babies grow fast and pants and sleeves can be rolled up if an item is too big for your little one.

Baby romper size

Baby clothes sizes charts

When it comes to baby clothes, not all sizes are the same. That’s why it’s always important to check each brand’s size charts to make sure you pick out clothes that fit right the first time. And to make things easy, we’ve put together a list of all the top baby clothes brands with sizing.

OskKosh Sizing¹:

Label / SizeWeight (pounds)Height / Length (inches)
P (Preemie)Up to 6 lbsUp to 18”
N (Newborn)6 – 9 lbs18 – 21.5”
0 – 3 months3-6 months21.5 – 24”
3 – 6 months6-9 months24 – 27”
6 – 9 months6-9 months27 – 28.5”
9 – 12 months9-12 months28.5 – 30”
12 – 18 months25 – 28 lbs30 – 32”
18 – 24 months28 – 30 lbs32 – 34”
2T29 – 31 lbs35 – 36.5”
3T31 – 33 lbs36.5 – 39”
4T34 – 37.5 lbs39 – 41.5”
5T37.5 – 42 lbs41.5 – 44”

Amazon Essentials Sizing²:

Label / SizeWeight (pounds)Height / Length (inches)
P (Preemie)Up to 5 lbsUp to 17”
N (Newborn)5 – 8 lbsUp to 20”
0 – 3 months8 – 12.5 lbs20 – 23.5”
3 – 6 months13 – 16.5 lbs24 – 25.5”
6 – 9 months17 – 20.5 lbs26 – 27.5”
9 – 12 months21 – 23.5 lbs28 – 30.5”
12 – 18 months24 – 26.5 lbs31 – 32.5”
18 – 24 months27 – 30 lbs33 – 34.5”
2T24 – 29 lbs33 – 35”
3T29 – 33 lbs35 – 38”
4T33 – 37.5 lbs39 – 41”

Gerber Sizing³:

Label / SizeWeight (pounds)Height / Length (inches)
P (Preemie)Up to 5 lbsUp to 17”
N (Newborn)5 – 8 lbs17 – 21”
0 – 3 months8 – 12 lbs21 – 24”
0 – 6 monthsUp to 16 lbs17 – 26”
3 – 6 months12 – 16 lbs24 – 26”
6 – 9 months16 – 20 lbs26 – 28”
9 – 12 months20 – 24 lbs28 – 30”
12 – 18 months24 – 28 lbs30 – 32”
18 – 24 months28 – 32 lbs32 – 34”
2T28 – 32 lbs32 – 34”
3T32 – 35 lbs34 – 38”
4T35 – 39 lbs38 – 40”
5T39 – 43 lbs40 – 44”

Old Navy Sizing⁴:

Label / SizeWeight (pounds)Height / Length (inches)
XS (P, N)Up to 7 lbsUp to 18”
0 – 3 months7 – 12 lbs19 – 23”
3 – 6 months12 – 17 lbs23 – 27”
6 – 9 months17 – 19 lbs27 – 28”
6 – 12 months17 – 22 lbs27 – 29”
12 – 18 months22 – 27 lbs29 – 31”
18 – 24 months27 – 30 lbs31 – 33”
2T30 – 33 lbs33 – 36”
3T33 – 36 lbs36 – 39”
4T36 – 40 lbs39 – 42”
5T40 – 46 lbs42 – 45”
6T46 – 53 lbs45 – 49”

Cat & Jack Sizing⁵:

Label / SizeWeight (pounds)Height / Length (inches)
NewbornUp to 7.5 lbsUp to 19.6”
0 – 3 months7.5 – 9.8 lbsUp to 21.5”
3 – 6 months12.3 – 15.4 lbs23 – 25.2”
6 – 9 months16.5 – 18.3 lbs25.9 – 27.2”
9 – 12 month19 – 21.7 lbs27.8 – 30.3”
27.8 – 30.3”22.2 – 24.1 lbs30.7 – 32.4”
18 – 24 months24.5 – 27.9 lbs32.8 – 34”
2T25 – 29.2 lbs34.2 – 35.4”
3T29.5 – 33 lbs35.7 – 38.5”
4T34.1 – 36.7 lbs38.7 – 40.8”
5T37 – 39.8 lbs41 – 42.6”

Carter’s Sizing⁶:

Label / SizeWeight (pounds)Height / Length (inches)
PRE (Preemie)Up to 6 lbsUp to 18”
NB (Newborn)6 – 9 lbs18 – 21.5”
3 months9 – 12.5 lbs21.5 – 24”
6 months12.5 – 17 lbs24 – 27”
9 months17 – 21 lbs27 – 28.5”
12 months21 – 25 lbs28.5 – 30”
18 months25 – 28 lbs30 – 32”
24 months28 – 30 lbs32 – 34”
2T29 – 31 lbs35 – 36.5”
3T31 – 33 lbs36.5 – 39”
4T34 – 37.5 lbs39 – 41.5”
434 – 38.5 lbs40 – 42.5”
5T37.5 – 42 lbs41.5 – 44”
4 – 538.5 – 43 lbs42.5 – 45”

How long do babies fit in newborn clothes?

This will depend on your baby, but typically infant clothing sizes fit for 4-6 weeks after you bring him home from the hospital. It can be confusing to determine the difference between Newborn and 0-3 month clothes, but typically Newborn sizes cover babies in the 5-8 pound range while the 0-3 month sizes fit 8-12 pound children. Each baby is different and grows at their own pace, so don’t be alarmed if your baby quickly outgrows Newborn sized clothes. If your little one is in a higher percentile for weight or height, they may even be wearing 0-3 month clothes home from the hospital!

How to buy baby clothes?

Try before you buy When possible, shop for baby clothes in person. This will allow you to see and feel the clothes and get an idea for the size of something before you buy. Just because your baby fits into a 3-month romper in one brand doesn’t mean she will in another, so shopping in person can prevent unwanted purchases.

Size up As a rule of thumb, it’s best to buy big. Your baby will grow quicker than you think and you can always roll up sleeves or pants on too-big items and let your baby grow into them over time. Who knows… you may find that an item that is at first too-big fits just right after a run through the wash.

What fabric is used for baby clothes?

When it comes to fabrics for baby rompers, soft materials are the best option. Cotton is a popular fabric used for baby rompers since it is lightweight and breathable, making it comfortable for babies to wear. Organic cotton is a great option as it’s free of harsh chemicals and toxins that could cause skin irritations. Other fabrics like bamboo and microfiber are also becoming increasingly popular for baby rompers since they’re lightweight, breathable, and offer natural wicking properties.

Polyester is another fabric used in baby rompers because it’s lightweight and has a nice feel to it. However, some parents may prefer avoiding polyester as it can be less breathable and hold onto odors more easily. Whichever fabric you choose, make sure it is comfortable and breathable for your little one.

Frequently Asked Questions About Baby Clothes

What else should I consider when shopping for baby clothes?

Pay careful attention to the material and stitching used, not just the size. Clothes made from 100% cotton will be more prone to shrink in the wash, so don’t be afraid to buy big. Inspect stitch and fabric quality as well. Low-quality stitching and fabric are more prone to fall apart in the wash after just a few cycles.

What’s the difference between 24 month and 2T sizes?

24-month outfits are designed for children still in diapers while 2T is more focused on potty-trained toddlers. While there may be slight differences in actual size, a 24-month onesie with multiple buttons can be tough for parents and children to undo for the potty. 2T clothes tend to feature more zippers and elastic waistbands, so it’s easier for your child to use the bathroom.

How many clothes do you need in each size?

This will depend on how quickly your baby grows, your laundry schedule, and whether dressing in layers is needed. Wintertime babies will need more items to bundle up in, paying special attention to foot and head coverings. If your family only does laundry once or twice a week, this will also affect how many outfits you need as babies often wear several outfits a day. Below are some general guidelines that can be adjusted based on your own personal needs.

0 – 3 month – Plan on two outfits and a sleeper each day, but don’t overbuy in this range as your child will grow quickly.

3 – 6 month – Plan on one to two outfits a day plus a sleeper. You may also need bibs for drooling.

6 – 9 month – Plan on one outfit and a sleeper each day.

9 – 12 month and beyond – One outfit and pajamas each day.

Kids clothing set matching

Buying clothes for your baby is exciting and fun, even if it’s a little confusing at first. Now that you know how to read size labels and have explored some of the brands available to your child, keep what you’ve learned in mind as you begin to prepare. Shop in person and follow your checklist to prevent overbuying and unwanted purchases from making it into your baby’s closet and dresser drawers!

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