Choosing the right-size baby clothes for your little one seems like it should be simple enough — in theory. Baby clothes are typically sized by age, so you'd think you would just buy pieces that correspond to your baby's age and that would be it.

Unfortunately, that's not always how it works. Like adults, infants come in all shapes and sizes. And different brands of baby clothes are not consistently sized the same way.

So if you're feeling lost when it comes to baby's clothing sizes, you're not alone. Here are a few tips to keep in mind when shopping or organizing baby's closet.

Baby clothes size chart

Depending on the baby clothing brand, some styles can run big, small or just right.

This baby clothes size chart (made using tips from real parents, countless online reviews and intel from What to Expect editors who've road-tested the brands at home with their little ones) can help you figure out how different baby clothing brands will actually fit your child, regardless of how big or small she is for her age.

baby clothes fit chart

How do baby clothes sizes work?

Baby clothing sizes can be based on a variety of factors, including:

  • Age

  • Weight

  • Length

That said, most baby clothing sizes are broken out based on averages. And because babies grow at different rates, not all 5-month-olds will fit into size 3-6-month clothing, for example.

So how do you know which size will fit your baby best? When it's time to create or update your little one's wardrobe, these strategies can help:

  • Do your research. As our baby clothing sizes chart demostrates, different brands of baby clothing is sized differently. Certain brands run smaller or larger, longer or shorter. Be sure to check each brand's website for their specific size chart to double-check where your baby's measurements fall on their sizing chart before you buy.

    Continue Reading Below

  • Know what the labels mean. Many parents will tell you (after experiencing this first-hand) a good rule of thumb is that the size on the label is often the max size. For example, size 3 months often means that it fits babies up to 3 months of age. Most 6-month-old babies wear 9- or 12-month-size clothing.

  • Consider fabric type. From spit-ups to blowouts, your baby may go through multiple outfits a day — which means more laundry. Keep in mind that fabrics like cotton, while comfortable, are prone to shrinkage, so it may be wise to go up a size.

  • Shop in person. That way you can eyeball the outfit to see if you think it might fit your little one, regardless of what the tag says, and go with your gut. When in doubt, size up — babies grow quickly, so it's better to buy clothing they'll have room to grow into.

  • Don't be afraid of trial and error. Because of the aforementioned size discrepancies from brand to brand, you may want to bite the bullet and try out a variety of different clothing brands to see which ones fit your baby's body best. Once you've established which brands fit your baby well, moving up to the next size as they grow can get a little easier.

Baby clothes sizes by weight

Most U.S. clothing brands base their sizing on average baby weight at a given age. While exact measurements can vary by brand, here's a general guide for baby clothing sizes by weight:

  • P (Preemie): Up to 5 pounds

  • NB (Newborn): 5 to 8 pounds

  • 3 months: 8 to 12 pounds

  • 6 months: 12 to 16 pounds

  • 9 months: 16 to 20 pounds

  • 12 months: 20 to 24 pounds

  • 18 months: 24 to 28 pounds

  • 24 months: 28 to 30 pounds

  • 2T: 29 to 32 pounds

  • 3T: 32 to 35 pounds

  • 4T: 35 to 39 pounds

  • 5T: 39 to 43 pounds

How many baby clothes do I need in each size?

Babies need a lot of stuff — with clothing at the top of the list. To avoid overwhelming yourself (and overspending), shop for baby in baby steps. Start by putting together a layette, or a set of clothing essentials, for the newborn days, which often consists of:

  • 4 to 8 shirts

  • 4 to 8 onesies

  • 7 one-piece footed pajamas

  • 3 to 6 one-piece rompers

  • 2 to 4 two-piece outfits (shirt and shorts/pants combinations)

  • 1 to 3 seasonal dress-up outfits

  • 4 to 8 pairs of socks or booties

  • 1 to 2 sweaters (for cold-weather babies)

  • 1 snowsuit or bunting (for winter babies)

  • 1 to 3 hats (knit hats for winter babies; sun hats for summer babies)

  • 1 to 2 swimsuits (for summer babies)

While that's a good place to start, you can choose to buy more or less depending on your situation — babies tend to need more layers in colder weather, for example, and how often you plan to do laundry should also factor into the equation.

Newborn baby clothes sizes

Whether you're looking for the perfect outfit to bring your baby home in, or just filling up little one's closet with an adorable wardrobe, it's important to think about which size to stock up on for the newborn days.

It may seem like common sense to buy the "Newborn" size for your newborn, but it's actually smarter to size up (slightly). On average, "Newborn" clothes only fit babies up to 8 pounds — which for most babies, doesn't last that long (and some babies even enter the world larger than that!).

Whereas size 0-3 months should fit your baby up to 12 pounds, and you can always roll up sleeves and pant legs for a few weeks while baby grows into the larger size.

If your baby is predicted to be petite, or you have a preemie, Newborn or Preemie sizes make a little more sense. Just consider keeping the tags on tiny outfits and hanging on to receipts in case baby arrives larger than expected or grows super quickly.

European baby clothes sizes

Picture this: You get an adorable baby outfit gifted to you, and you check the tag to see what size it is, but it simply says "70." Just when you think you understood baby clothing sizes, you're hit with the European sizing system.

European baby clothing sizes are labeled based on maximum centimeters in height — meaning a size 70 should fit a baby up to 70 centimeters, or around 27.5 inches long (though there's a range). As with U.S. sizes, when shopping European baby clothing, it's important to review the exact brand's size chart.

Here's a general guide for what European baby clothes sizes typically translate to in the U.S.:

Size 60 in baby clothes

A good rule of thumb is that a European size 60 is equivalent to U.S. size 3-6 months. This size will typically fit a baby who is 12 to 16 pounds, or 22 to 26 inches long.

Size 70 in baby clothes

Size 70 in Europe is similar to a 6-12 month size in the U.S. It should fit babies who are 16 to 20 pounds, or 26 to 28 inches long.

Size 80 in baby clothes

A European size 80 is about the same size as 12-24 months in the U.S. It likely fits babies ranging from 20 to 27 pounds, or 28 to 32 inches long.

Size 90 in baby clothes

Size 90 in Europe ranges is about a size 2T in the U.S. It should fit a toddler who weighs between 26 and 33 pounds or up to a height of 36 inches.

Size 100 in baby clothes

A European size 100 is about a 3T (and up to 4T) in the U.S. It'll likely fit a toddler weighing between 31 and 38 pounds, or up to a height up to around 40 inches.

Cracking the baby clothing sizes code can be tricky. A good rule of thumb: When in doubt, size up. And remember, within no time (and after a little trial and error), you'll be a pro at discovering which clothing sizes and brands work best for your little one.