How To Choose The Right Crib Mattress Size: The Complete Guide

baby sleeping on crib mattress

With a baby on the way, you’re likely going to spend a lot of time designing a nursery and making decisions about everything from paint colors to storage. But some decisions impact more than design. The correct crib mattress size, for instance, can impact your baby’s safety.

In this article, the experts at Newton Baby discuss the types of cribs and their corresponding crib mattress sizes so that you can make an informed decision for your new little one.

Table of contents

Crib Types: Advantages And Disadvantages

Crib sizes

The color and style of the crib you choose for your baby’s nursery are important, but size is another critical factor to consider. Here are a few guidelines to keep in mind when making your decision about which type of crib to purchase.

Standard Cribs

Standard crib dimensions

A standard-sized crib is the typical go-to for most parents. Measuring around 28 inches by 52 inches, standard cribs are significantly larger than mini cribs.

While a standard (or regular) crib is often more expensive than a mini crib, the biggest advantage of a regular crib is that your child will get several years of use out of their baby bed.

Standard cribs feature mattress bases that can be lowered. When your baby is a newborn, the mattress is placed at the highest level so they can be attended to easily. Lower the mattress when they can sit, and then again when they can stand so that your little one is safe and secure.

Many standard cribs can be converted into toddler beds, so you won’t need to buy a new bed once your child discovers how to escape from their crib. But if you decide to switch things up and buy your little one a fun toddler bed, you can purchase a toddler bed frame and use the same standard crib mattress.

3-In-1 Cribs

The 3-In-1 Crib adds an extra bit of functionality to the standard crib. When configured as a crib, the 3-in-1 uses the same crib mattress size as a standard crib.

However, when your baby grows out of the crib, a 3-in-1 design can not only convert to a toddler bed with the addition of a toddler conversion kit, but it comes with extra pieces to convert it into a twin bed (requiring a Kids’ Twin Mattress) as well.

This type of bed can take your baby all the way through to their teenage years! And although a 3-in-1 design is more expensive than a standard crib, it offers so many more years of use that it may be well worth it.

However, if you want the flexibility to freshen up the room with new design choices as your child grows, this may not be the best option for you. In addition, you would have to store the extra pieces until you’re ready to use them, which could take up more space than you want.

Mini Cribs

mini crib dimensions

You can probably guess the advantages of a mini crib just from its name. At 24 inches wide and 38 inches long, the mini crib is smaller than a standard-sized crib. This small size is especially useful if your nursery is short on space.

Additionally, mini cribs are ideal if your new baby will be sharing a bedroom with their older sibling or if you’re putting two cribs in the same nursery for twins. You can also purchase a mini crib to leave at grandma and grandpa’s house to make overnight stays more convenient.

If you need a portable crib that can easily roll around the nursery, choose a mini crib with wheels. Just be sure the wheels are locked and the crib is securely in place when you’re not moving it.

Although they’re similar, don’t confuse a mini crib with a bassinet. The key to a mini crib’s extended use beyond the bassinet months is that the base of the crib can be lowered as your baby grows. This is an important feature to keep your little one safe while they’re sleeping or awake.

Finally, compared to standard cribs, mini cribs are easier on your wallet. But before you make your decision based on that fact alone, remember that your baby will outgrow their mini crib — usually around two years old or, sometimes, earlier. At that point, you’ll need to buy a bigger bed to fit your growing toddler.

Shaped Cribs

Baby standing up in his white shaped crib

As with all baby items, there’s no shortage of adorable touches and unique additions when it comes to cribs. While standard and mini cribs are rectangular, some cribs are available in special shapes — like circles or ovals — and have mattresses to match.

These cribs are a good option if you want to add a unique design element to your baby’s nursery. Shaped cribs are often smaller than standard ones, though, so keep that in mind while you’re crib shopping.

And just like the crib mattress follows the shape and size of your crib, so do the sheets. You get the most choice of crib sheets and mattresses with standard-size cribs.

So, if you’re leaning toward a shaped crib instead, take a peek at the array of mattresses and sheets that can go with it before making your final decision.

Bassinet Cribs

baby sleeping in bassinet

A bassinet crib is the most compact choice, perfect for newborn babies. These are easy to put next to your bed, something that is recommended by the American Academy of Pediatrics. That way, you can keep your baby close for nighttime feedings or dream feedings if you so choose.

However, because bassinet cribs are so small and the base of the bassinet can’t be lowered, when your baby can push themselves up on their hands and knees, sit up, try to rock the bed, turn over in their sleep, or are simply too tall, it’s time to move to a mini crib or crib.

Design Notes

Although most design considerations are a matter of taste, there is one thing to consider when choosing your crib beyond simple aesthetics. Namely, the view.

Some cribs have spindles all the way around, making it easy to see your baby from any angle. Others have solid sides that, depending on the crib position, can block the view for both parent and child.

Choose a crib where you can easily see your little one so you can be sure they are safe and cozy as they drift off to dreamland.

Choosing The Right Crib Mattress Size

two different crib mattress sizes

Once you have picked out the best crib for your baby, all that’s left to do is to choose the right mattress. While this may seem easy, there are a few things to consider as you shop. The first thing to know is the difference between mattress sizes.

When it comes to crib mattress sizes and the safety of your baby, you want to be sure that the mattress fits inside the crib snugly with as little space as possible between the two. A large gap can pose a safety risk for your baby.

As a rule, when the mattress is inside the crib, you should not be able to fit more than two fingers between it and the crib frame. But let’s talk more specifically about each crib mattress size.

Crib Mattress Size: Standard

standard crib mattress size


As you might guess from the name, the standard crib mattress is the typical mattress size for baby cribs.

According to the Consumer Products Safety Commission, a standard (or regular) crib mattress should be no more than 6 inches thick and measure at least 27 1/4 inches wide and 51 1/4 inches long.

Tips For Selecting The Right Standard Crib Mattress

If you have a standard-sized crib for your little one to snooze in, you’ll need a standard-sized crib mattress.

As we mentioned, the size of these mattresses is regulated. However, there is a bit of wiggle room within the regulated size of a crib. A standard crib can be ⅝ of an inch larger or smaller than the regulated 28 by 52 ⅜ rectangle.

A standard mattress will typically fit a standard crib, but because of this small variation, you will still need to check to make sure your mattress fits properly — not too big and not too small.

Here’s an example: If your crib is on the large side of the regulated measurements and your mattress is on the small side, you may end up with a gap in-between the mattress and the crib. Always check the fit before putting your baby in bed for the first time.

Crib Mattress Size: 3-In-1


This is easy: A 3-in-1 crib will take the exact same mattress as the standard crib. Since the 3-in-1 can also convert into a twin bed, you will have to choose a twin mattress when the time comes. The US-standard twin mattress size is 38 inches wide and 75 inches long.

Tips For Selecting The Right 3-In-1 Mattress

Look to our guidance on choosing the right crib mattress size for a standard crib above, as this will be the same for a 3-in-1 crib.

After the 3-in-1 crib has done its job for the baby and toddler years, it’s time to reconfigure it as a twin.

When looking for a twin mattress for this stage of your 3-in-1 crib, there aren’t the same safety concerns as there are for babies. However, you will want to choose something that’s hypoallergenic, breathable, and easy to clean with firm support for growing bones.

Crib Mattress Size: Mini

mini crib mattress size


Coming in smaller than the standard crib mattress is the mini crib mattress. The government does not regulate the size of mini crib mattresses as they do for standard ones. However, the typical size is 24 inches wide and 38 inches long.

Tips For Selecting The Right Mini Crib Mattress

While you can likely purchase most mini crib mattresses and expect them to fit your mini crib, you’ll still want to double-check the fit because some mini cribs are narrower than others.

Mini crib mattresses are also available in different depths, so be sure to research the dimensions before making a decision.

Crib Mattress Size: Shaped


There are no standard specifications or government regulations for shaped crib mattresses. Shaped cribs vary in size and most will likely come with a mattress.

Tips For Selecting The Right Shaped Mattress

If you have a specially shaped crib, the same rule applies for the mattress: not too big and not too small.

If your shaped crib does not come with a mattress, you’ll want to use a tape measure to determine the appropriate size and then choose a mattress that fits snugly inside your crib without too much room around the edges.

Crib Mattress Size: Bassinet


Like the shaped crib mattresses, there isn’t a standard for bassinet mattresses. Generally, the purchase of a bassinet will include a mattress that’s just right.

Tips For Selecting The Right Bassinet Mattress

As we mentioned above, a perfectly-sized mattress is normally included with bassinet cribs. If it isn’t, don’t worry. Just measure the crib with a tape measure and choose a mattress that meets the two-finger rule.

Crib Mattress Compatibility

It’s important to purchase a crib mattress that meets your country’s standards. For instance, a standard European crib mattress is smaller than a standard North American crib mattress and, therefore, will not provide a safe sleeping environment in a crib meeting U.S. standards.

You don’t have to worry when choosing a mattress for a standard crib that was purchased from a retailer in the U.S., though. The issue of crib/mattress mismatch generally comes up with vintage cribs, cribs purchased overseas, or cribs purchased on a resale marketplace.

If you don’t know what size mattress you need, don't fret. First, consult your product manual. That should give you all the dimensions you need. If you don’t have the manual, break out your measuring tape and measure length and width. Subtract about ½ inch to account for the two-finger rule.

Tips For Crib Safety

We’ve already talked about choosing the right crib mattress size for your baby’s crib. But here are just a few more tips to make sure your baby gets the safest sleep possible.

  • The best position for babies to sleep is on their backs. Whether you’re putting them down for a mid-afternoon nap or the night, never place them on their side or their stomach.
  • Don’t use products for sleep that aren’t specifically intended for that purpose. Sleep products must comply with specific Consumer Product Safety Commission (CPSC) regulations to ensure safe sleep.
  • Babies should not be placed on an incline as this can be dangerous.
  • Ensure there are no blankets, pillows, stuffed toys, or bumper pads in the baby’s crib. If your baby rolls into them while sleeping, these items could block proper airflow.
  • You should not share your bed with your little one, as this can be dangerous. However, it is recommended that you room share with your baby for the first year of life. According to the American Academy of Pediatrics, room sharing can decrease the risk of SIDS by 50%.

Beyond Crib Mattress Size: Additional Tips For Choosing A Crib Mattress

woman holding her sleeping baby

As you begin to explore the world of crib mattresses, you’ll realize that size is not the only factor that differentiates one mattress from another. You’ll need to keep a few other factors in mind.


First of all, crib mattresses should be firm. While your older child might appreciate a soft and cozy bed, when it comes to your infant, the firmer the mattress the better. Soft mattresses can increase the safety risks for young babies.

It’s important to note, however, that “firm” does not necessarily mean hard. Traditional crib mattresses are rock-hard because, in order to prevent a baby's head from sinking in and to avoid suffocation risk, they are encased in non-breathable plastic.

By making the Newton mattress completely breathable, we were able to make it much more comfortable as well — without any risk of suffocation.

To be sure you have a firm crib mattress, push down on it and see if it immediately springs back into place when you take your hand away.


Secondly, consider going with a breathable crib mattress. This is important because non-breathable mattresses may increase the risk of suffocation for young babies.

However, you can put yourself at ease with a breathable mattress, like Newton Baby’s Crib Mattress, which allows air to flow freely for optimal breathability and temperature regulation while your little one sleeps.


Newton Baby’s Crib Mattress is made with patented Wovenaire® technology and zipped into a comfortable, washable, and breathable mattress cover.

In fact, you can get the most out of your breathable mattress by using Newton Baby’s Waterproof Crib Mattress Pad and skipping the sheet. The mattress pad is durable, comfortable for your little one, and machine-washable. It’s as easy as that!

Non-Toxic And Allergen-Free Materials

As your baby spends lots of time on a crib mattress, the materials used must be as safe as possible.

Fire Retardants

All mattresses have to abide by strict flammability regulations, which often involve the use of chemicals. However, some mattresses meet those standards with natural materials rather than chemicals.

At Newton Baby, we take a chemical-free approach to safety. We use a layer of viscose material — made of reconstituted wood pulp — instead of chemicals. The viscose material is sewn into the cover or a separate, inner encasement is placed under the cover.

We’re also mindful of common allergens and make sure we don’t include irritants like foam, latex, springs, or glue in our mattresses. Instead, Newton Baby Crib Mattresses are made of safe, food-grade polymer.

GREENGUARD Gold Certification

Another thing to look for when shopping for a crib mattress is the GREENGUARD Gold certification. Our mattresses meet these strict requirements, signifying that the mattress exceeds the highest industry safety standards.

The Truth About Organic Mattresses

Although, at first blush, you may think that an organic mattress is the safest, you should know there can be hidden dangers.

Organic mattresses are often sealed in airtight plastic covers, making them not breathable. This can be a real safety hazard for your baby.

In addition, organic mattresses are not washable, meaning it’s easy for dust mites, mold, and bacteria to gather. Newton Baby’s Crib Mattresses, on the other hand, balance safe, washable materials (with no toxic chemicals or allergens) with breathability.


Now we get to practical matters: cleaning. When choosing a mattress, you want to find one that’s easy to clean and maintain.

The Newton Baby Crib Mattress is the only crib mattress that’s entirely washable from cover to core. Say “goodbye” to dirt, dust, and allergens, and “hello” to sleep!


You don’t want to have to go to the gym just to lift your mattress. When your baby grows, you’re going to have to lower the mattress, which means it’s a little more tricky (and requires a little more muscle) to pull out the mattress and remove the crib sheet when it’s laundry day.

A lighter mattress will make this task easy-breezy. Our crib mattresses range from 11-14 pounds, which is considered quite light.


More than ever, environmental impact matters. You can breathe easy when it comes to Newton Baby Crib Mattresses, as all of our mattresses are recyclable.

Another option is upcycling your crib mattress. We partnered with Figgy to offer this new idea: Just get an extra cover and pillows and convert your crib to a play couch. How fun is that?

Home Trial

Although we can sing the praises of the Newton Baby Crib Mattress all day long, the best thing to do is to try it. We offer a 100-night home trial so your baby can get some zzzs on the mattress in the comfort of their own crib.

As you prepare for your baby’s arrival, check one thing off your list and put your mind at ease by choosing a Newton Baby Crib Mattress designed with your baby’s health, safety, and comfort in mind.

And, as we mentioned above, every mattress made by Newton Baby is 100% breathable, 100% washable, and 100% recyclable.

Smiling baby on a Newton Baby crib mattress

With a little knowledge and the tips we’ve listed here, you can have a pretty, functional crib and crib mattress that are comfortable enough for baby to rest well and safe enough to put your mind at ease.

Browse all nurseries