The Ins and Outs of Baby & Toddler Clothes Sizes

There are many things to learn when preparing for baby, and if you’re brand-new to parenthood, you know that sizing baby clothes is one of them! While baby clothes are typically sized in a relatively straightforward manner, there are things that you should know before loading up on the basics. In this guide, we’ll help you understand baby sizing conventions so you know how to buy the right sizes and how to prepare for your little one’s frequent growth spurts.


The Basics: Babies Grow at Their Own Pace

In general, baby clothing is sized by age. Newborn clothing is marked as NB (for newborn), infant clothing is marked by month (for example, 0-3M) and toddler clothing is marked by age (for example, 2T for two-year-olds). But there are some hiccups with this convention. Ask any seasoned parent and they’ll probably tell you that their baby’s clothing didn’t perfectly match his or her age. Maybe they wore newborn clothing well into their third month or maybe they were already in 3-6M at 9 weeks old.

For this reason, it’s important that you’re paying close attention to other factors, primarily your baby’s height and weight. When purchasing new baby clothes after baby is born, reference the brand’s size chart and purchase the size that corresponds to baby’s height and weight rather than their age. The fact of the matter is that babies grow at their own pace, so you’ll get a much more accurate fit when you go off your bundle’s size and not their age.

Gerber Childrenswear - Baby Onesies® Bodysuits

You already know that a comfy, cozy baby is a happy baby, so finding the right fit is an important part of the process. Make sure that you pick baby clothes and Onesies® Bodysuits that are snug but not tight—especially around the neckline and leg openings—so that baby doesn’t get irritated throughout the day. When your bundle becomes mobile, it’s important that you pick clothes that don’t restrict their range of motion when they’re dancing, running and spinning in circles at the playground.

Preparing for Baby: How Much of Every Size Do I Need?

When you’re getting ready to welcome a new baby, determining how to stock the closet is a monumental task. Having a rough idea of how much of every size you need will help ensure that you’re not over or understocked. It will also help you guide friends and family so they don’t shower you with too much of one size! Remember that there is simply no way to know exactly how quickly your baby will grow or how often he or she will need a change of clothes, so allow yourself to estimate rather than plan exact sizes

During the early stages of baby’s life, she’s changing at a rapid pace. She’s also making messes more often. In the newborn and infant phases, make sure you have extra Onesies® Brand bodysuits and sleepers. We recommend having at least 15 Onesies® Brand bodysuits and seven sleepers on hand in each size if you do laundry once per week—that accounts for at least two outfits a day and one set of pajamas every night, which can be worn again without laundering if baby wakes up clean and dry.

Gerber Childrenswear - footie pajamas with food theme

Once your little one starts to walk, there’s a good chance she’ll have playdates, preschool and other events where you need more than just a couple of plain Onesies® Brand bodysuits and pajamas. Plus, as baby grows, there will be fewer messes and daily outfit changes, so you can begin to create a more varied wardrobe. Introduce toddler playwear once they start walking—three per week is good, but purchase based on how often baby will need to dress for playdates and outings.

Gerber Childrenswear - Mix and Match Outfits & Sets


Sizing Gerber Childrenswear Baby Clothes

Preemie to Toddler

Size Weight Height
Preemie  Up to 5 lbs. / Up to 2.3 kg Up to 17 in. / Up to 43.2 cm
Newborn (NB) 5-8 Ibs. / 2.3-3.6 kg 17-21 in. / 43.2-53.3 cm
0-3M 8-12 Ibs. / 3.6-5.4 kg 21-24 in. / 53.3-61 cm
0-6M Up to 16 Ibs. / Up to 7.3 kg 17-26 in. / 43.2-66 cm
3-6M 12-16 Ibs. / 5.4-7.3 kg 24-26 in. / 61-66 cm
6-9M 16-20 Ibs. / 7.3-9.1 kg 26-28 in. / 66-71.1 cm
12M 20-24 Ibs. / 9.1-10.9 kg 28-30 in. / 71.1-76.2 cm
18M 24-28 Ibs. / 10.9-12.7 kg 30-32 in. / 76.2-81.3 cm
24M / 2T 28-32 Ibs. / 12.7-14.5 kg 32-34 in. / 81.3-86.4 cm
3T 32-35 Ibs. / 14.5-15.9 kg 34-38 in. / 86.4-96.5 cm
4T 35-39 lbs. / 15.9-17.7 kg 38-40 in. / 96.5-101.6 cm
5T 39-43 lbs. / 17.7-19.5 kg 40-44 in. / 101.6-111.8 cm

Cotton Pajamas

Garments are designed to fit snug for child's safety.
Size Weight Height
6M 12-16 Ibs. / 5.4-7.3 kg 24-27 in. / 61-68.6 cm
12M 16-20 Ibs. / 7.3-9.1 kg 27-30 in. / 68.6-76.2 cm
18M 20-24 Ibs. / 9.1-10.9 kg 30-33 in. / 76.2-83.8 cm
24M / 2T 24-28 Ibs. / 10.9-12.7 kg 33-35 in. / 83.8-88.9 cm
3T 28-32 Ibs. / 12.7-14.5 kg 35-39 in. / 88.9-99.1 cm
4T 32-36 Ibs. / 14.5-16.3 kg 39-42 in. / 99.1-106.7 cm
5T 36-42 Ibs. / 16.3-19.1 kg 42-44 in. / 106.7-111.8 cm

At Gerber Childrenswear, we make it simple to size clothing based on baby’s size so you find perfectly fitting clothes at any age. Make sure to reference our size guide above for information on sleepwear, clothing and Onesies® Brand bodysuit sizing. If you aren’t sure which size will suit your baby, feel free to contact us and we’d be happy to assist you with sizing. 

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