What Size Is a Standard Crib Mattress? 4 Facts to Know

The number one concern parents have when welcoming a new baby is safety, and more importantly, sleep safety. Purchasing a crib mattress can be confusing so this guide can help you narrow your choices from the correct crib mattress size to firmness, breathability and more.

Standard Crib Mattress Size

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The United States Consumer Product Safety Commission states that a standard crib mattress size is 27 1/4 inches x 51 1/4 inches with a thickness not exceeding 6 inches. These regulations help keep your baby safe and reduce the risk of your baby from getting stuck between the crib mattress and crib rails.

But size is just one thing to look for with a mattress. Here are some other tips to help you out when choosing the best crib mattress for your baby.


A crib mattress should provide your baby with a firm,  flat sleeping surface. This is particularly important when your infant becomes more mobile and active.  they will need a firm surface to push up on, turn, and even stand in their crib. Soft sleeping surfaces and loose bedding should be avoided since they can create  suffocation hazards for infants and increase the risk of Sudden Infant Death Syndrome (SIDS).

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Having a breathable mattress can help your infant sleep longer, safely, and more sound. A mattress made with porous materials allows for good airflow which can  help reduce sleep disruptions due to heat and allows the baby to breathe freely through the mattress even if he rolls onto his stomach. The most breathable crib mattresses are made with innerspring coils and organic comfort layers like wool, cotton and coconut coir.

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Built with Organic Materials

The National Sleep Foundation recommends that infants in their first year of life sleep approximately 12-17 hours per day. That is a great deal of time spent on their crib mattress, so making sure it is as healthy as possible is important. Invest in a mattress that is organic and free of toxic chemicals.  Be sure to Look for the GOTS (Global Organic Textile Standard) or GOLS (Global Organic Latex Standard) certification. Whenever possible avoid flame retardants, polyurethane, and vinyl in all of your baby products.

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Choosing the Correct Crib Accessories

Once you’ve made your crib mattress selection, you should also look into protecting your investment with an organic waterproof mattress protector.

A crib mattress protector can protect your mattress from moisture, dust mites, and other allergens. Just add an organic cotton fitted crib sheet and  your baby will be ready for a healthy night’s sleep. . Just like when purchasing your crib mattress, it is important to look for the GOTS certification when purchasing a mattress protector and sheet set.

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Crib Mattress Size FAQs

What are the standard crib mattress dimensions?

A standard crib mattress size is 27 ¼ inches x 52 inches. 

Why are crib mattress dimensions important?

To reduce any risk to your infant while sleeping, making sure that the crib mattress is the standard dimensions is very important. Having gaps between the mattress and the crib side is hazardous. Finding a mattress that fits snug into a crib is essential.

What is the difference between a crib mattress and a toddler mattress?

A toddler mattress typically has the same dimensions as a crib mattress. The main difference between the two is the firmness. It is important for a crib mattress to be firmer than other size mattresses to reduce the risk of SIDS in infants.

What is the right time to switch to a toddler bed?

On average most children make the transition to a toddler bed between 18 months and 3 years old, depending on the child’s readiness to transition.

Why do I need a crib mattress protector?

Not only does a waterproof crib mattress protector protect against dust mites, moisture, and other allergens, but it also provides a more sanitary environment for your infant.