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Onesies and Bodysuits

How to Choose the Right Onesie Size for Your Baby

How to Choose the Right Onesie Size for Your Baby

As a new parent, it can be difficult to know what size clothes to buy for your little one. Babies grow so quickly and you don’t want to waste money on outfits that will only fit for a short time. When it comes to onesies and bodysuits, it’s important to choose the right size for your baby’s comfort and safety. Here are some tips on how to choose the right onesie size for your baby.

1. Consider Your Baby’s Age

The age of your baby is a good place to start when it comes to choosing the size of your onesies. Most brands label their bodysuits and onesies sizes by age, so a 0-3 month onesie will fit most babies up to three months old. Keep in mind that not all babies grow at the same rate, so it’s best to use age as a starting point and then assess your baby’s size and shape.

2. Look at the Weight Measurements

Babies’ weights can vary greatly and can be a more accurate way to determine the right onesie size. Most brands provide weight ranges for each size, so you can compare your baby’s weight to the recommended size. For example, if your baby weighs 10 pounds, a onesie labeled 0-3 months and fitting babies up to 12 pounds might work well.

3. Check the Height Recommendations

Height can also be a helpful way to choose the right size of onesie for your baby. Some brands provide height ranges in addition to age and weight recommendations. If your baby is particularly tall or short for their age, height recommendations might be the most helpful in finding the right fit.

4. Choose the Right Fabric

The type of fabric can also affect how well a onesie fits your baby. Some fabrics, like cotton, can shrink in the wash, so it’s important to factor in potential shrinkage when choosing a size. Other fabrics, like stretchy materials, might be more forgiving when it comes to size and fit.

5. Assess Your Baby’s Body Shape

Babies come in all shapes and sizes, so it’s important to assess your baby’s body shape when choosing a onesie size. Some babies have long torsos or chubby legs, which might affect how well a onesie fits. It’s a good idea to try on different sizes and styles to see what fits your baby’s body best.

6. Consider Buying a Size Larger

Some parents prefer to buy onesies a size larger than their baby’s current size. This can help extend the life of the onesie and allow for more room to grow. However, keep in mind that clothes that are too big can be uncomfortable and potentially unsafe for your baby. It’s important to find a balance between comfort and room to grow.


Choosing the right onesie size for your baby involves considering their age, weight, height, body shape, and fabric type. It’s important to find a onesie that fits well and allows for comfort and movement. By keeping these tips in mind, you can find the perfect onesie for your little one.

FAQ: How to Choose the Right Onesie Size for Your Baby

What size onesie should I buy for my newborn?

Newborns typically wear size 0-3 months onesies. The size will say “NB” or “newborn” on the tag. However, keep in mind that every baby is different and may grow at a different rate, so it’s always a good idea to have a few different sizes on hand.

How do I know if a onesie is too small?

If a onesie is too small, it will be tight and uncomfortable for your baby. You may notice that the snaps are difficult to fasten or that the fabric is stretched to its limit. Your baby may also seem irritable and fussy while wearing the onesie.

How do I know if a onesie is too big?

If a onesie is too big, it will be loose and may bunch up or hang off your baby’s body. The neckline and armholes may be too big, which could cause the fabric to rub against your baby’s skin and cause irritation. Additionally, the excess fabric may make it difficult for your baby to move around comfortably.

Should I size up with onesies?

It’s generally a good idea to have a few onesies in the next size up on hand for when your baby outgrows their current size. However, it’s not necessary to size up with every onesie purchase. Babies grow quickly and it’s impossible to predict exactly when they’ll move on to the next size, so it’s best to play it by ear.

What if my baby falls in between two sizes?

If your baby falls in between two sizes, it’s best to go with the larger size. This will allow your baby to grow into the onesie and get more use out of it before it no longer fits.

Do different brands of onesies run differently in size?

Yes, different brands may run differently in size. It’s always a good idea to check the size chart for the specific brand you’re buying to ensure the best fit for your baby. Additionally, some brands may be more suited to certain body types, so it may take a bit of trial and error to find the right onesie for your baby.

How often should I be buying new onesies for my baby?

Babies grow quickly, so it’s likely that you’ll need to purchase new onesies every few months. However, it’s not necessary to go overboard with your purchases. It’s best to have a few different sizes on hand to accommodate your baby’s growth.

What types of closures should I look for in a onesie?

There are two main types of closures for onesies: snaps and zippers. Snaps can be more difficult to fasten and unfasten, but they allow for easier access for diaper changes. Zippers are easier to open and close, but may not allow for as easy access for diaper changes. It ultimately comes down to personal preference and convenience.

What fabrics are best for baby onesies?

The best fabrics for baby onesies are soft, breathable materials like cotton or bamboo. Avoid fabrics that are scratchy or irritating to the skin, as well as those that don’t provide enough ventilation.

Should I be concerned about the neckline of a onesie?

Yes, the neckline of a onesie is important to consider. Make sure that it’s not too tight or too loose, as either can be uncomfortable or irritating for your baby. Additionally, look for onesies with envelope or expandable necklines, as these will allow for easier dressing and undressing.

Related Products

  • Measuring Tape: One of the most important tools when it comes to measuring your baby for the correct onesie size is a measuring tape. These tapes come in a range of sizes, and they allow you to easily measure your baby’s height, waist, and chest circumference. It’s recommended to use a measuring tape that is soft and flexible, so as to avoid hurting your baby while measuring.
  • Baby Growth Chart: A baby growth chart is essential for any new parent. They come in a range of sizes and styles, and they’re designed to help you track your baby’s growth over time. This not only helps you choose the right onesie size, but also helps you ensure that your baby is growing as expected. A growth chart can be hung on the wall and is a great way to record your baby’s development.
  • Baby Onesies: Once you’ve measured your baby and determined the correct size, you’ll want to stock up on baby onesies. Onesies come in a range of sizes and styles, and they’re one of the most practical items of baby clothing. They’re easy to put on and take off, and they also feature a range of designs and features such as snap buttons that make changing your baby a breeze. Look for onesies made from soft, breathable materials such as cotton, and ensure they have easy to open snaps for diaper changes.
  • Baby Pants: In addition to onesies, you’ll also need a range of baby pants in different sizes. These are great for layering and keeping your baby warm in cooler weather. There are a variety of styles available, including leggings and joggers as well as traditional pants. Look for pants that feature an elasticated waistband and cuffs, as these will help keep your baby comfortable and prevent them from slipping off.
  • Baby Socks: Keep your baby’s feet warm and cozy with a range of baby socks. These are perfect for wearing with onesies or pants and are available in a range of styles and colors. Look for socks made with soft, breathable materials, and ensure they have a non-slip sole to prevent slips and falls. You’ll also want to stock up on several pairs, as babies often outgrow them quickly.
  • Baby Hats: To keep your baby’s head warm and protected, you’ll want to invest in a range of baby hats. These come in a range of styles and sizes, and they’re essential for protecting your baby from the sun or cold weather. Look for hats made from soft, breathable materials such as cotton, and ensure they have a good fit with gentle stretch – for your baby’s comfort.
  • Baby Blankets: Babies need blankets for cuddling, sleeping, and even as a changing mat. There are several styles of blankets that you can opt for such as receiving blankets, swaddling blankets, and fleece blankets, all designed for different purposes. A receiving blanket is generally the first blanket that is used for wrapping your baby after birth. A swaddling blanket is designed for swaddling your baby, while a fleece blanket is perfect for colder weather. Look for blankets made from soft, breathable materials, and ensure they are machine washable and easy to clean.
  • Baby Bath Tub: A baby bath tub is an essential item for new parents. Look for models that are sturdy and designed with safety and support in mind. These tubs are perfect for bathing small babies and come in a range of sizes and shapes. Look for models that have a non-slip bottom with a comfortable incline to support your baby during bath time. Some models also come with additional features such as a built-in thermometer to ensure the water temperature is safe for your baby.
  • Baby Lotion: Keeping your baby’s skin moisturized and soft is essential. Look for baby lotions that are gentle and formulated for delicate skin. These lotions come in a range of scents and are perfect for daily use. Look for lotions that are free from harsh chemicals such as parabens, sulfates, and phthalates.
  • Baby Diapers: No baby or parenting-related list is complete without mentioning diapers. A baby’s skin is delicate and prone to rashes, so it’s important to choose diapers that are gentle and breathable. Look for diapers with a high absorbency rate, and ensure they come with leak-proof sides to prevent any accidents. There are several types of diapers available, including disposable and cloth. Choose the option that works best for you and your baby.

Pros & Cons: How to Choose the Right Onesie Size for Your Baby


  • Comfort: Choosing the right size onesie can ensure that your baby is comfortable and has enough room to move around freely.
  • Prevents overheating: An ill-fitting onesie can trap heat and cause your baby to overheat. Choosing the right size can prevent this.
  • Reduces risk of suffocation: A onesie that is too big can cause your baby to get tangled up and pose a risk of suffocation. Choosing the right size can prevent this.
  • Cost-effective: Choosing the right size onesie can save you money in the long run, as you won’t need to keep buying new ones as your baby grows out of them too quickly.
  • Easy to put on and take off: Choosing the right size onesie can make it easier for you to dress and undress your baby, as a onesie that is too small can be difficult to get on and off.


  • Can be difficult to choose: Choosing the right size onesie can be difficult, especially if your baby is between sizes or is growing at a rapid pace.
  • May need to try on multiple sizes: To ensure that you get the right size, you may need to try on multiple sizes, which can be time-consuming and frustrating.
  • May need to purchase more frequently: If your baby grows quickly or is in between sizes, you may need to purchase new onesies more frequently, which can be expensive.
  • Not all brands are the same: Different brands may have varying sizes and fits, which can make it difficult to know which size to choose.
  • Can be a safety hazard: A onesie that is too small can be a safety hazard, as it can restrict your baby’s movement and cause discomfort or even injury.

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