Preemie clothes

Baby clothes sizes, explained: What you need to know to buy babies of all sizes

It shouldn’t be complicated, but for some reason baby sizes on clothes are confusing, especially if you don’t have a frame of reference. (“Can newborns wear size 0-3 clothes?” “And why isn’t that the same as newborn size?!”) And what makes things more confusing It’s the fact that, just like the clothes themselves, there’s no one-size-fits-all rule when it comes to determining which clothes from which brands will fit your baby when.

“It’s impossible to give hard and fast rules when it comes to sizing baby clothes, especially since brands size and label things a little differently,” says Jenn Bonnett, a fashion and wardrobe stylist who mainly works with the children. “Also, all children are different sizes, regardless of age, so it’s important to keep in mind that the sizes we see are based on the average. If your baby is in the 99th percentile, you will need to size up.”

“It’s impossible to give hard and fast rules when it comes to sizing baby clothes, especially since brands size and label all things a little differently.”


But even in the absence of a universal guide for baby clothing sizes, there are some general rules that will make shopping for a onesie a lot more fun than stressful. Here, the experts break down the confusing world of baby clothing sizes.

Is the newborn the same size as 0-3 months?

“Newborn size represents an average baby at birth up to 21.5 inches long and 5 to 8 pounds, which can be a very wide range,” says Dr. Amna Husain, Pediatrician at Pure Direct Pediatrics in Marlboro Township, New Jersey.

In terms of weight compared to 0-3 month clothes, the range is usually 8-13 pounds, according to Husain, but there are other considerations to take into account, namely length.

“Babies come in all shapes and sizes, so the range is useful if you have a baby on the smaller/smaller side versus the taller/longer side,” Husain says. “I’ve found sorting clothes by length versus what the label says can be helpful as some brands are small and some are large.”

How long do babies last in newborn clothes?

Whether you’re trying to pick out a homecoming outfit for your own little one or picking out something sweet for a loved one’s new baby, newborn (NB) size clothes or something a little bigger with room to grow, like 0-3 months, is probably the way to go. Which one will fit right off the bat? Ultimately, it depends on the size of the baby, which is almost impossible to predict before birth.

“I recommend having a variety of sizes on hand for your newborn, including newborn and 0-3 months,” says Husain.

While babies are known for their ability to grow — and outgrow clothes — at lightning speed, Husain notes that not everyone will pack newborn-sized clothes after a week or two. “You can have your little one wearing newborn clothes for 4-6 weeks if they’re closer to the 4-5 pound range,” Husain points out. “Every baby is different, but it’s a good idea for parents to remove tags and wash some, not all, newborn clothes before birth. This way they can be flipped if baby goes up a size quickly.

“I recommend having a variety of sizes on hand for your newborn, including newborn and 0-3 months.”


Use the same line of thought if you’re buying clothes for a newborn or a baby shower gift. Size NB clothes may not fit for long – and some larger babies may never get a chance to wear them – so it’s safest to buy a size or two for newborns.

Explanation of baby clothing sizes

Just as caring for babies gets easier over time, so does cracking the DaVinci code of buying clothes for them. Not only will it become more obvious which end of the height and weight spectrum your child is on, but you’ll also become familiar with how favorite brands work.

“While a lot of choosing the right size baby clothes comes down to a particular brand, my personal rule is to consider the label to mean ‘up to,'” Husain explains. “So if a label says ‘3 months’, I think it can hold 0-3 months, or if it says ‘6 months’, it can hold 3-6 months.” Husain notes that while this rule won’t necessarily work for every garment and every brand, it will simplify shopping until parents have an idea of ​​baby’s shape, as well as brand preferences.

“My personal rule is to consider the label to mean ‘until’. So if a label says ‘3 months’ I think it can hold 0-3 months, or if it says ‘6 months’ , it can last between 3 and 6 months.


Here’s a real-life example: Baby Gap’s 3-6 month size range fits babies 12-17 pounds and 23-27 inches, while Carter’s 3-month-old clothes fit babies 9-12.5 pounds and 21.5 to 24 inches and their 6 month clothes fit babies 12.5 to 17 pounds and 24 to 27 inches. The difference between 9 and 12 pounds is significant in babies.

Besides having a few NB pieces set aside before baby is born, as a general rule, it’s always a good idea to size up when you don’t know baby’s exact height. For example, when shopping for clothes for a 3 month old child, opt for the 3-6 month (or larger) size range instead of the 0-3 month range.

A few other good reasons for the size rule? Clothes may shrink in the laundry over time, but babies will continue to grow.

“My son was getting too big for his clothes, so one day in a rush I grabbed some Cat & Jack rompers from Target in what I thought were his size,” notes Mia Perez, a mother of three from Howell, New Jersey. “They ended up being super big on him. After a few weeks – and many washes – they did eventually adjust, though. And in fact they have shrunk so much that my next baby was able to wear them on the first side.

Los Angeles mom of two Cheryl Delfino had a similar experience with her first baby. “For the first few months of my daughter’s life, she lived in simple Gerber onesies, so when I received a gift card for Baby Gap, I was thrilled to use it,” says Delfino. “I bought a bunch of rompers and onesies online in 3-6 months and they were huge! Eventually she grew into them but my daughter was swimming in them when she was 3-4 months.

“Not only do children’s clothes shrink the more you wash and dry them,” says Bonnett, adding that it’s all the more reason to buy clothes with room to grow, “but kids are just plain cute in oversized sweatshirts or pullovers with the sleeves rolled up — and they get extra length and more wear that way.

The moral of the story? If you’re still unsure which sizes are best for your baby or if you’re trying to buy a gift for someone else, it’s a good idea to refer to a brand’s size chart as it there are always variations. And when in doubt, go up a size, knowing baby can get bigger.

To help you out, we’ve compiled some of the best baby brands and sizes.

Baby clothing size chart by brand*


Label/size weight in pounds) Height/Length (inches)
P (Premature) Up to 6 pounds Up to 18″
NB (newborn) 6-9 pounds 18-21.5″
3 months 9-12.5 pounds 21.5-24″
6 months 12.5 to 17 pounds 24-27″
9 months 17-21 pounds 27-28.5″
12 months 21-25 pounds 28.5-30″
18 months 25-28 pounds 30-32″
24months 28-30 pounds 32-34″

Amazon Essentials

Label/size weight in pounds) Height/Length (inches)
P (Premature) Up to 6 pounds Up to 17″
NB (newborn) 6-9 pounds Up to 21.5″
3 months 9-12.5 pounds 21.5-24″
6 months 12.5 to 17 pounds 24-26.5″
9 months 17-21 pounds 26.5-28.5″
12 months 21-25 pounds 28.5-30.5″
18 months 25-28 pounds 30.5-32.5″
24months 28-30 pounds 32.5-34″


Label/size weight in pounds) Height/Length (inches)
Premature Up to 5 pounds Up to 17″
Newborn (NB) 5-8 pounds 17-21″
0-3 months 8-12 pounds 21-24″
0-6 months Up to 16 pounds 17-26″
3-6 months 12-16 pounds 24-26″
6-9 months 16-20 pounds 26-28″
12 months 20-24 pounds 28-30″
18 months 24-28 pounds 30-32″
24 months/2T 28-32 pounds 32-34″

Old Navy & Baby Gap

Label/size weight in pounds) Height/Length (inches)
Up to 7 pounds Up to 7 pounds Up to 18″
0-3 months 7-12 pounds Old Navy 19-23″
Baby gap 18-23″
3-6 months 12-17 pounds 23-27″
6-9 months Old Navy 17-19 lbs.
Baby gap 17-20 pounds
6-12 months Old Navy 17-22 lbs.
Baby gap 20-22 pounds
Old Navy 27-29″
Baby gap 28-29″
12-18 months 22-27 pounds 29-31″
18-24 months 27-30 pounds 31-33″

Target brands (including Cat & Jack, Cloud Island)

Label/size weight in pounds) Height/Length (inches)
Premature up to 5.5 pounds up to 17.5″
New born 6-8 pounds 18-20″
0-3 months 9-12 pounds 20.5-23.5″
3-6 months 12.5 to 16 pounds 24-25.5″
6-9 months 16.5 to 19.5 pounds 26-27.5″
9-12 months 20-23 pounds 28-30.5″
18 months 23.5-26 pounds 31-32.5″
24months 26.5 to 28 pounds 33-35.5″
* According to the size charts on the brands’ sites at the time of this publication.

What is the difference between 24 months and 2T?

If you’re wondering about one of the biggest mysteries in baby clothes – what’s the difference between 24 months and 2T – the answer is pretty concrete: it’s mostly about fashion and whether a child is potty or nope.

“The biggest difference between size 24 months and 2T is style,” says Jessica Herman, director of customer experience at children’s clothing subscription service KIDBOX. “The 2T size generally corresponds to more mature toddler styles, where the 24 month size has more baby-friendly garments, such as onesies, especially suitable for children who are still in diapers.”

In other words, it’s much easier for a child or parent to get a pair of pants on and off when it’s potty time, rather than unzipping a jumpsuit. Additionally, some brands, like Baby Gap, even note that in addition to providing extra room in their garments for a diaper, their sizes are representative of garments with a diaper.

While it would certainly be handy if baby sizing was as easy as following a label, alas, few things related to parenthood are that simple. That said, once you find what works best for your little one, it’s easy. Until then, however, prevention is better than cure. “Whenever you’re not sure about the size, always take the next size up,” says Herman. “Children are constantly growing, and it’s better to be too big than too small.”