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9 onesies for babies of all ages in 2021

We consulted experts about what makes a good baby onesie, plus got their sizing advice.
Three images of cute babies wearing different onesies
Babies will outgrow onesies quickly as they age, which means it’s important to keep several different options on hand.Getty Images

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Whether you’re a parent-to-be or are shopping for one, there’s one classic baby apparel essential that’s hard to debate: the onesie. And when it comes to the divisive world of parenting, most parents agree that one onesie simply isn’t enough. Experts consider them a quintessential baby shower gift, especially since parents will need them in a range of sizes as well as styles. “You need a lot of them as it’s the most basic staple in a baby’s wardrobe and what you dress them in every day,” said Jennie Monness, mom of two and co-founder of play space Union Square Play. “When you have them on hand, there is little thought you need to put into dressing your baby each day. They take the thought out of the dressing process.”

No matter the weather, onesies are an easy outfit choice for those early weeks or months. “In warmer weather they can be an entire outfit (especially under a swaddle blanket) and in colder weather, they're excellent as an undershirt,” explained Talitha Phillips, a certified labor and postpartum doula and CEO of Claris Health. Plus, they fit securely on babies and don’t require a ton of work when frequently dressing, undressing and changing a child throughout the day.

Onesies come in many different sizes, and babies will outgrow them quickly as they age and grow. We spoke to experts to learn more about what to know about onesies, plus got specific onesie recommendations and found other highly rated options based on their guidance.

SKIP AHEAD Onesies and bodysuits to shop

How to shop for baby onesies and bodysuits

Sizing for onesies is typically organized by either age or weight, which means it doesn’t account for a baby’s girth, explained Jada Shapiro, a birth and postpartum doula and founder of Boober, a marketplace of classes for moms. Although each brand is different, shoppers will typically find onesies sold in this range of sizes:

  • Preemie (uncommon)
  • 0-3 months
  • 3-6 months
  • 6-9 months
  • 9-12 months
  • 12-18 months
  • 18-24 months
  • 2 years

Since you don’t necessarily want to take your baby shopping with you and have them try on each onesie in the fitting room, experts recommend sticking with certain brands and assessing where your baby fits in each brand’s sizing chart. The sizing varies greatly by brand and doesn’t always strictly correlate to a baby’s exact age — a 2-month-old can easily rock something that’s for 3-6 months and a little one could be ready for the 12-18 months options from one brand even if they are only 9 months old.

How do you know when a onesie fits? Mainly, you want to make sure there’s some room at the snap between the legs so you don’t need to pull the material to button, explained Monness. Instead, you want extra material there for easy closure. Onesies should be fitted, but not too tight around the neck or legs. “You’ll know they’re too small if they’re leaving red marks on your baby’s body,” Shapiro noted.

Onesies and bodysuits to shop

Here are some of the best onesies and bodysuits across sizes and styles, most of which are expert-recommended. We also included a handful of top-rated options compiled based on expert guidance.

Best overall gender-neutral onesie: PiP PEA POP

The Babysuit

This 100 percent GOTS-certified organic pima cotton long sleeve “babysuit” is Monness’s favorite because of how thoughtful every single feature and design element is. “There’s both a zipper and snaps so you can open and close [it] in the most convenient way for you (and the most comfortable way for your child),” she said. Plus, there are no tags or itchy seams, it comes with foldable footies depending on preference and it has elongated design so your baby can fit in it for a long time.

Best budget-friendly white onesie: Gerber

Gerber Unisex-Baby 8-Pack Short Sleeve Onesies Bodysuits

With these 100 percent cotton onesies, you get a fuss-free classic that will match everything at a reasonable price point. They also come in a long sleeve pack as well as in long sleeves with foldover mitten cuffs. With a snap-crotch closure and expandable neckline, Monness agreed that you can’t go wrong with this onesie.

Best preemie onesies for the NICU: Perfectly Preemie

Ahoy Long Sleeve Nic-jumpsuit

When a little one is born prematurely and staying in the Neonatal Intensive Care Unit (NICU), you have to take both their small size and easy accessibility for wires into consideration when trying to find clothing that they can wear. Perfectly Preemie was created by a NICU family who understands the needs of preemie babies, especially those in the NICU, Shapiro explained. Designed to actually fit babies weighing 3-6 pounds, the brand’s line of preemie options is made from 95 percent cotton and meets all NICU requirements.

Best onesies for newborns and 0-3 months: Kissy Kissy

White Pointelle Long Sleeve Bodysuit

Made from 100 percent pima cotton, everything from this brand is incredibly soft, which is one of the things Monness loves about them. Plus, they have a diverse range of options, with everything from long sleeve onesies with mitten cuffs and printed footies to the classic short sleeve onesie. However, Monness noted that Kissy Kissy’s onesies do tend to run small — this is great for those shopping for a tiny new addition, but it’s important to keep in mind when determining which size to order.

Top-rated onesies for 3-6 months: Monica and Andy

Essential Baby Zipper Bundle

Monica and Andy’s essential baby zipper bundle is an ideal baby shower gift option — it comes with a bodysuit, footie, long sleeve onesie and short sleeve onesie to keep parents covered as their little one starts growing out of their newborn gifts. Made from 100 percent GOTS-certified organic cotton, these soft onesies and bodysuits are available in a range of 60 different colors and prints.

Best onesie for 6-9 months: Magnetic Me

In-dog-nito Ii Modal Magnetic Coverall

Everything from Magnetic Me closes with hidden magnetic fasteners instead of buttons or zippers. According to Monness, this makes them more convenient to put on and take off for any age, but particularly when shopping for the 6-9 months size as this is typically when babies start solids and “diaper changes can get out of hand.” Phillips also raved about this brand — she especially loves the onesie set with harem pants as a chic option for this age. However, Monness noted that the magnetic closures can be loud in the washing machine and can catch you off guard if you aren’t expecting them.

Best onesies for 9-12 months: Burt's Bees

Moonlight Clouds Organic Baby Zip Front Loose Fit Footed Pajamas 3 Pack

This set of three footies is made from 100 percent organic GOTS-certified cotton with a diagonal zipper for quick changes and a tab to hide that zipper from little fingers. These play and sleep footed pajamas come in a range of playful prints and have a non-slip bee grip on the feet. Monness explained that this is the size when little ones tend to start cruising and eventually walking, so that extra detail matters.

Top-rated short onesies with matching options: Little Sleepies

Sweet Pea Floral Bamboo Viscose Shorty Zippy

This onesie is made from soft bamboo viscose that can keep babies cool during the summer and warm during colder months. This short style works for both day or night and comes in a range of playful patterns with matching options for siblings as well as mom or dad. It features a simple zipper instead of snaps or buttons.

Top-rated splurge baby shower onesie bundle: Monica and Andy

Motherlode Modern Layette Cuddle Box

With 33 pieces and 58 mix-and-match combinations in a range of sizes, this gift box of 100 percent GOTS-certified organic cotton pieces will keep parents covered when it comes to onesies, pajamas and bodysuits needed throughout a baby’s first year. Available in gender-neutral as well as smaller bundle options depending on price point, these curated gift boxes are both thoughtful and practical.

Different onesies and bodysuit styles: What to know

In addition to different leg and sleeve lengths, shoppers will typically come across several different styles of onesies, according to Shapiro.

  1. Snap crotch. These onesies have traditional snaps at the crotch.
  2. Shoulder fold. This style gives additional room if needed in the shoulder area to make removal easier — it can come in handy when changing a messy blowout.
  3. Wraparound or kimono. These onesies close shut at the baby’s side and are secured with either a side tie or snaps down the side.
  4. Snaps down the front (both legs). This style has snaps that go down the front and then split, requiring snaps down both legs. Though it’s harder to put on with more snaps, it gives parents more access to each leg.
  5. Side snaps down the front (one leg). These onesies require snapping down the front at a slight angle and across only one leg.
  6. Zipper. You can find some onesies that zip down the front and others that zip down one leg.
  7. Magnetic. Convenient for parents, these onesies skip the tedious snaps and have self-closing magnets instead.

Onesie versus bodysuit versus sleeper

In basic terms, a standard onesie is a one-piece, close-fitting outfit that typically has either short or long sleeves, no leg coverage and a snap crotch that fits over a baby's diaper, Shapiro explained. Although she noted that many people consider onesies and bodysuits to be the same thing, “a bodysuit is [more commonly] a onesie with legs, providing full body coverage.” A sleeper or footie, meanwhile, typically refers to something that’s similar to a bodysuit with covered feet — it’s also usually made from a heavier weight to keep the baby warm at night. A sleeper can also be something that’s similar to a onesie that the baby wears almost like a sleeping bag.

There’s also the onesie/bodysuit crossover that has short sleeves and short legs. “This is great because a baby can move freely and feel the sensations of things like the floor on their body (which helps them process the world),” explained Monnes. This “allows a baby who is developing gross motor skills every day to move their limbs and grip the ground securely to learn to roll, scooch, crawl and eventually walk most securely.”

What to consider while shopping for a onesie

The experts we spoke to noted that there are more things to consider when shopping for a onesie beyond size and style. Below, we highlighted a few factors to keep in mind as you look for onesies for your little one.

  • Color. Although onesies come in every color and print imaginable, whites and neutrals are popular because they match everything (which comes in handy when you’re changing your baby multiple times a day).
  • Material. Keep an eye out for softer and more breathable materials, including organic cotton, lightweight muslin, stretchy spandex and bamboo. Monness specifically recommended GOTS certified pima cotton, noting that it’s “super soft and ethically made.” “It’s certified organic cotton baby clothing produced in environmentally and socially responsible conditions, having a low impact on nature and human beings by reducing direct exposure to hazardous chemicals,” she explained.
  • Hand covers. These can flip over tiny hands to act as mittens and keep little fingers from scratching their faces.
  • Footies. These keep feet warm during the night and some have anti-slip grips on the bottom to help keep walkers from slipping and sliding.

The perks of onesies

Despite some having little snaps that can be pesky, onesies have cemented themselves as a staple in a baby’s wardrobe. One of the reasons parents love them is because the design prevents them from riding up, keeping the baby’s belly and back from being exposed. “The onesie essentially functions like a well-tucked shirt,” said Shapiro. “They are comfortable, stretchy, safe, easy to use and don’t roll up like a T-shirt would.”

This added layer of protection also comes in handy if a baby has older siblings. “Parents also like that they keep the diaper contained and prevent the older child from taking off their diaper,” added Shapiro.

How many onesies do parents need?

Having lots of onesies is helpful for new parents because as “babies spit up, pee and poop a lot, you will likely find your baby’s onesie is wet or dirty a million times a day,” Shapiro noted. “Having a lot of onesies will help keep your baby dry and fresh without you having to do laundry multiple times per day.”

But with the speed in which little ones grow, it can be difficult to know how many onesies to have on hand in each size. Shapiro recommended a range of 7-14 onesies or bodysuits in each size grouping depending on whether parents have easy access to laundry. “More if you don’t, less if you,” she said.

In the beginning, babies go through at least four outfit changes per day due to diaper leaks, spills and spit ups, according to Monnes. Starting off with eight onesies may seem like a lot, but that equates to around just two days’ worth of clothes in the early months. However, if you plan on doing laundry daily (or close to it), you can get by with closer to 4-6 per size, according to Moss. Alternatively, you can plan on having more onesies during the newborn stage and fewer as they get older.

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