baby crib mattress

What Size Is a Baby Crib Mattress?

Written by: Melissa Loehle



Time to read 9 min

While shopping for the best crib for your little one’s nursery, don’t forget to also get them the best crib mattress you can!


Baby crib mattresses come in different sizes and styles, depending on the style and size of the crib you are purchasing. Whether you have your heart set on a traditional crib or a shaped one, be sure to read our tips to create the safest sleep environment for your baby. 

500+ 5-Star Reviews
Meet The Glider Plus
Ships immediately!
All the features
you need in our
Award Winning glider

What are the Different Types Of Crib Mattresses? 

When you are designing your nursery, the crib is one of the most essential items you will be shopping for. Cribs come in different styles and sizes, and it is important to have a crib mattress to match.


Some mattresses need to be bought separately, so be sure to have one on your checklist! Here is a breakdown of the different types of cribs and the crib mattress considerations that go along with them. 

crib vs mini crib mattress

Standard Cribs 

Standard crib mattresses must be, at minimum, 27 ¼ inches wide by 51 ⅝ inches long. Anything smaller can pose a safety risk. As with all crib styles, ensure that your little one’s crib mattress fits snugly inside their crib and that their crib sheet is tightly fitted. Most crib sheets are designed to fit standard crib mattresses. 


Standard crib mattresses are actually the same size as toddler mattresses. This eases the transition from crib to toddler bed, especially if you have a convertible crib.


With this style, you will need to replace the front bars with a separately purchased toddler rail. Nurture&’s standard sized crib is a convertible style, and a matching toddler guardrail is also available to add on when needed. 

standard crib mattress

Mini Cribs

Mini crib mattress sizes are not federally regulated, but the typical mini crib mattress size is 24 inches wide by 38 inches long. Due to the lack of regulation on size, the US Consumer Product Safety Commission (CPSC) does require that all mini cribs come with a mattress.


These mattresses are known to be thin, and you may be concerned by their flimsiness, but what is most important is that they are firm and breathable.

You should always ensure that your mattress fits snugly inside your baby’s crib, especially if you decide to purchase a separate mini crib mattress for any reason.


Also, be mindful not to use a mini crib mattress in any other size crib: mini crib mattresses can only be used in mini cribs. They are too small to fit a standard crib, and any gaps between the mattress and the crib sides pose a suffocation risk. If you purchase a mini crib, be sure that your mattress fits properly for safe sleeping. 

Shaped Cribs 

Shaped cribs come in a variety of special sizes. They can be round, oval, or even hexagonal. If you purchase a shaped crib, it is likely that it will come with the mattress, since the sizes of shaped cribs are not regulated.

You can buy a shaped crib mattress separately, but make sure that the dimensions fit exactly without gaps. Hexagonal is a more common shape for playards or playpens, but if you are using this shape of mattress for sleeping, make sure it’s firm and breathable. 

Explore The Nursery

How to Choose the Right Crib Mattress Size

Now that you know the different types of cribs and mattresses available, let’s get into the important details to help you decide which one is best for your little one’s nursery. 

crib mattress size

Standard Crib Mattress Size

Standard full-size crib mattresses are good for about five years. They are designed for use in both standard-sized cribs and toddler beds, so they will fit your child into the toddler years, as long as they are sleeping in a crib or toddler bed: Standard crib mattresses will not fit in twin beds. 


The style and design are more traditional, which makes it easier to find a suitable crib mattress size for your crib. 


A quality, firm, and breathable standard crib mattress may be slightly expensive, but they are long-lasting. You may also want to add a breathable or waterproof mattress pad. Nurture& has a curated selection of quality, nontoxic mattresses, mattress covers, and pads to help your search. 

Standar crib size

Due to their size and rectangular shape, these cribs are suitable for larger rooms that are at least 12 feet by 18 feet.


Sincestandard crib mattress dimensions are regulated, it is more common to sell them separate from the crib. 


Looking for a quality, nontoxic standard crib for your standard-sized mattress? Nurture&’s crib will last your child through age five and is made with premium and sustainable materials for peace of mind. 

Mini Crib Mattress Size

Both mini crib mattresses and standard crib mattresses  are rectangular, but they are not interchangeable. 


Mini cribs are also known as portable cribs, and they can have slatted or mesh sides. 


Mini cribs are smaller versions of standard cribs, but they are larger than bassinets. They must use a mattress designed for a mini crib. 


Mini cribs tend to be more affordable than shaped or standard cribs. They are even more affordable when you factor in that they typically come with the mini crib mattress too. 


Mini cribs are an excellent choice for homes with smaller rooms or without a separate nursery. They are compact enough for room sharing but still bigger than a bassinet, so they can be used for longer.  


If your mini crib does not come with a mattress, a matching mattress size may be sold separately, or you may need to find one from another retailer. Although mini crib sizes are regulated, check the dimensions of your mini crib and the mini crib mattress size before purchasing. 

Shaped Crib Mattress Size

Oval crib mattresses are common in bassinets, and hexagonal mattresses are more common in playpens. 

Round crib mattresses are a fancier option. The lack of corners may make them safer. However, round cribs are not the most practical. They do not occupy wall space, but this means they will not sit flush against a wall. They may be placed as focal pieces in the center of a nursery, or in a corner.


There are less options for shaped crib mattresses on the market, as most shaped cribs will come with their own mattresses. This means that if you are unhappy with the included mattress, you may have difficulty finding a suitable replacement. 


Shaped cribs and crib mattresses can be expensive, depending on the brand. 

How to Measure the Size of Your Baby's Mattress?

The dimensions listed for cribs are often the outer dimensions. To ensure a safe and proper mattress fit, you will need to find out the interior dimensions of the crib.

Crib mattresses are designed to be slightly smaller than the inner dimensions, but there should be no more than a one inch gap between the crib and the mattress.  If there is a large gap it can pose a safety risk to the baby for the possibility of entrapment and suffocation.

rectangular shape mattress

To choose the correct mattress height, you will base your decision on the total height of the crib. You want a minimum distance of 26 inches from the top of the mattress to the top of the side rail on the crib.

To help achieve this, purchase a mattress that is no more than six inches thick. If your crib allows for different mattress heights, remember to move to the lowest setting as your baby begins to move and pull up. 

Choosing a Crib Mattress 

When choosing the best crib mattress, there are a few important factors to consider, no matter what type of crib you choose. Below we have a list of the most important considerations. 


Firm mattresses are the safest. A firm mattress reduces the risk of suffocation and sudden infant death syndrome (SIDS). This is because a soft mattress may make it hard for a baby to move their head to get air. Their face may sink into the mattress if it is too soft. 


To test a crib mattress’s firmness, press on the center and the edges. If the mattress immediately returns to its original place, then the firmness is safe for your baby. Firm mattresses are also beneficial as babies learn to roll, push themselves up, and pull up to stand, by giving them a surface to move against that does not give. 


According to the Consumer Product Safety Commission, crib mattresses should not be more than six inches thick. This prevents your little one from being too close to the top of the crib. If your baby has less than 26 inches from the top of their mattress to the top of the crib, they are at risk of falling out of the crib as they learn to pull up and climb.


The typical crib mattress is 4 to 6 inches thick. A thicker mattress does not equal a better or safer mattress, as firmness and breathability are more important factors in safe sleep. 


You want to buy a quality mattress that is durable and will last as long as you need it. Avoid using secondhand mattresses if possible, as they may have experienced wear and tear that makes them less safe. Another reason to avoid secondhand mattresses is that you may be unable to verify their age, and crib mattresses have an average life of five years


Some mattresses may have a side that is firmer for use in a crib and a less firm side for use in a toddler bed, which increases their longevity. 


Breathable crib mattresses are mattresses that promote airflow within the bed. These are important for safe sleep and to prevent issues like overheating and disrupted sleep.


Many people prefer organic mattresses because they are free from chemical content. Look for a breathable and clean mattress by checking for certifications like GOTS (Global Organic Textile Standard) or Greenguard. 

Baby mattress

The Lullaby Earth Breeze Air Mattress features a non-toxic waterproof mattress with a removable washable, waterproof, and breathable cover. Another quality option is the Naturepedic Organic Breathable Lightweight 2-Stage Crib Mattress. This certified organic crib mattress also comes with a washable, breathable, and waterproof cover.


When it comes to purchasing a mattress, it's important to consider the cost versus the quality. While it may be tempting to skimp on price, investing in a high-quality mattress is a wise decision for your health and overall wellbeing.


Keep in mind that mattresses featuring non-toxic materials and waterproof, breathable covers typically come at a higher price point. However, the benefits of such a mattress make it a worthwhile investment in the long run.

While making the very important decision on your little one’s crib, you also need to consider the quality of the crib mattress. Check whether a mattress is included with your crib. Whether it is or not, we hope you can use these tips to pick out the best quality mattress to ensure safe sleep for your baby! 


For more quality crib and nursery products, check out Nuture&’s online store and discover more about our products and all things pregnancy and parenthood in our journal!

Melissa Loehle

Melissa Loehle

Melissa Loehle is an Educator, Graduate Intern, Writer, and Mother. She has experience teaching children in general education, English as a foreign language, and speech pathology. She is a former kindergarten teacher and is currently completing her masters in Communication Sciences and Disorders from Baylor University. Melissa has taught English as a volunteer and online. She is a freelance writer and editor who loves to help educate others. Her favorite accomplishment is becoming a mother. She is the mother of two boys, ages four years old and five months old, as well as a dog mom to two mixed breed oddballs. She currently resides in Saratoga County, NY.