What is The Standard Crib Mattress Size?

Putting up a nursery is one of the most important things a mother can give to her child. However, just like you, your child also needs a comfortable place where he/she can sleep and play.

When expecting the arrival of a new baby into the house, you might be preoccupied with buying other necessities, such as clothes, toys, bottles, and finally a crib. Many people put mattress shopping in the last place, because, well, it’s just a mattress, nothing to fuss about, right? The fact of the matter is that for a good (and safe) night’s sleep for your baby, choosing the right mattress is crucial. Are there any standards that you should look into when shopping for a crib mattress?

While you’ve probably suffered from the mattress you have purchased, you may possibly inclined to concede to a crib set for your baby and not consider much about it. Actually, giving you little one a safe and right crib mattress is very important. Since it is where your child stays for a couple of years.

But the question is, what would be the standard crib mattress size for babies. Thus, if you’re planning to buy a crib mattress and want to know the right crib mattress size for your baby, then this content is for you.

The Standard Crib Mattress Size

Unlike mattresses for adults, the size of a crib mattress really matters. As a matter of fact, crib mattresses’ size is specifically regulated by the industry as well as the federal government to make sure that your baby has a safe sleeping environment.

The CPSC or Consumer Products Safety Commission requires that full-size crib mattresses for babies must be at least 51 and 1/4 inches in length and 27 and ¼ inches in width. In addition, a crib mattress, on the other hand, must have a maximum thickness that is not more than six inches. When it comes to standard cribs, they must have a 28” x 52 3/8” interior rectangle.

While this might seem like a lot of precision and measuring for just a mattress, bear in mind that too big of a mattress might not fit into the crib, or fit wonky, which is not comfortable for the child to sleep on. Even so, the reason why the size of crib mattresses have been standardized under deferral regulations is that too small of a mattress might be a safety hazard, especially as babies start to develop and get more active.

When the crib mattress is too small, your child might roll off the mattress and get stuck between the frame of the crib and the mattress itself, posing a threat to injury, but also to suffocation, which is why the general rule of the thumb is that a crib mattress should be no more than two fingers, or one and a half inch, smaller than the frame of the actual crib.

When buying a new crib, most sellers provide mattresses that are sold as sets to that specific crib design. The problem arises when you are using an older, hand-me-down crib that might not be on sale any longer, or is maybe even hand-made.  If this is the case, you should precisely measure the dimensions of your crib and look for the closest model to that size to avoid any inconveniences.

Either way, the established standard crib mattress size, will safely and perfectly fit in full-sized cribs.

However, if you are planning to buy a crib mattress it is very easy to determine if your chosen model meets the standard size set by CPSC since the measurements are listed in the assembly instruction and in the retail box.

Other Important things to Consider When Buying a Crib Mattress

Aside from checking if a certain crib mattress meets the standard size, there are also other important things that you need to consider when shopping for one.

Depth and weight

As aforementioned, the CPSAI standard is that a mattress should not exceed six inches in thickness. The proportion of the mattress and it’s adjustment inside the crib solely depends on your child’s age and ability: once a child is old enough to sit up on its own, the mattress should be thinner and set lower into the crib to make it harder for the child to attempt to climb over the crib.

When it comes to depth and weight, you might be looking into something to ease your own work – foam mattresses are easier to lift when changing sheets rather than coil-spring mattresses, and they are also thinner in size, but coil-spring might provide more sturdy mattresses. This measurement depends on individual factors.


While you don’t want your baby to sleep on a rock-solid surface, and might prefer snuggling your little one into a bubble of softness and gentleness, bear in mind that this is not the way to go when taking a crib into consideration.

When not being held, the best solution for the healthy development of your baby’s bones is for them to sleep on a firmer surface, ensuring that they will sleep flat down and not bent over, which can cause problems in the long run. Aside from the long-term effects, take into consideration that your baby needs more support than you do – a baby has around 300 bones, which gradually fuse together when entering adulthood.

A firmer mattress ensures more skeletal support for the developing soft structure of your baby, especially its spine. Additionally, a soft mattress may, on the same level as too small of a mattress, be a choking hazard and increase the risk of SIDS (Sudden Infant Death Syndrome) which most commonly comes from suffocation when the baby rolls over during their sleep.

If your baby completely sinks into the mattress that it’s on, chances are, you will constantly have to monitor their movement during sleeping to ensure that their head is always facing up.

An easier way to test the firmness is to use your fingers to press the mattress (both at the center and at the edges) and see how fast it snaps back once you release it. If it takes a significant amount of time, you might want to avoid that mattress if your baby is still too small to roll back up on its own.

Look for a crib mattress that is stable as it reduces the possibilities of suffocation as well as offers a safe and comfortable sleeping platform.

Cost and Quality

Not all expensive crib mattresses are great and not all inexpensive models have poor quality. That is why, when buying a mattress make sure to check its quality (you can check our guide to make sure you know the essential information when choosing a crib mattress) . If you think it is too costly then check if it is made of high-quality materials and safe for your baby and the same goes through to cheap models.

You do not want to save up when buying anything for your little one, but some crib mattresses seem very overpriced, and getting a second-hand mattress or choosing a cheaper one might seem more appealing.

It is, however, not advised to buy very old second-hand mattresses as they might become too soft, dented, and simply worn down with time. Additionally, a mattress is hard to clean completely, and some children might even require an allergen-reducing cover or organic material, which might cost extra.

When it comes to standard crib mattresses, however, the cost doesn’t necessarily equal quality. You can have a 200 dollar mattress that is too soft and thin, while a 90 dollar mattress might be just the perfect fit for your baby and its crib. Buying a new mattress according to your individual factors might be the best possible solution.

In addition to the firmness, cost, and quality, when buying a crib mattress you should also consider the ease of cleaning, durability, support, breathability, and comfort.


While crib mattresses might be the last thing on your mind when stacking up for the arrival of your baby, it’s definitely a necessity to bear in mind that your baby will spend a lot of his/her time inside that crib sleeping, so you want to ensure that the environment is safe and comfortable for your child – measure your crib, choose a mattress that correctly fits it, pick a mattress with an appropriate thickness and firmness, and put your child’s needs in front of your own preferences. A healthy baby is a happy baby, after all.

We hope that this article will help you a lot in choosing the right crib mattress for your baby. Nevertheless, when buying for one make sure that the mattress meets the standard size which is 27 ¼ inches (width) by 51 ¼ inches (length).