Crib Mattress Dimensions: Everything You Need to Know About Crib Mattress Size

If you're in the market for a crib mattress, make sure to pay attention to dimensions. Standard crib mattresses are 28 inches by 52 inches, but you should measure your crib before purchasing to ensure a proper fit. Mini cribs require smaller mattresses, typically 24 inches by 38 inches. Portable cribs also require smaller mattresses, but the dimensions can vary by brand. It's important to choose a mattress that fits snugly in the crib without any gaps between the mattress and the crib walls. Additionally, choosing a firm mattress can help reduce the risk of suffocation and SIDS.

As a new parent, there are so many items you’ll need to purchase for your little one, but one item that tops the list is a

crib mattress.
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There are a surprising number of crib mattresses to choose from, so it can help to start with this informative guide that shares the standard crib mattress dimensions along with tips on how to choose the right crib, and mattress, for your bundle of joy.

illustration showing crib mattress dimensions

“If your baby is sleeping in a crib or bassinet, a mattress is essential,” says Ariana Witkin, MD, board-certified pediatrician and postpartum coach. And it’s important to make sure you use the correct size for the crib or bassinet in use.

“The mattress should fit snugly in the sleep environment and there should be no gaps—there should be less than an inch between the mattress and the crib when the mattress is pushed up against one side,” says Witkin.

Below, find everything you need to know about crib mattress dimensions and the various types of crib mattresses out there, as well as answers to your most common questions about crib mattresses.

Crib mattress dimensions

A standard crib mattress size comes in at 28 inches x 52 inches. Although this is the most common crib mattress size, there are other, less-popular crib mattress sizes to note, such as the mini crib mattress, which measures 24 inches x 38 inches.

Also, crib mattresses don’t always come in customary rectangle shapes—sometimes, they’ll come in circular, oval, and hexagonal shapes, which are more for aesthetic value than anything else.

illustration of crib mattress showing the dimensions

Crib mattress dimensions are regulated by the United States Consumer Product Safety Improvement Act of 2018 (CPSIA). One of these safety precautions says that crib mattresses should be no more than six inches thick to prevent accidental falls.

Unit of MeasurementCrib Mattress Dimensions
Inches28 x 52 in
Feet2.3 x 4.3 ft
Centimeters71 x 132 cm
Meters.71 x 1.32 m

Other factors to consider when choosing a crib mattress

Besides dimensions, there are a few other essential factors to think through when purchasing a crib mattress.

First is firmness. Witkin notes that The American Academy of Pediatrics (AAP) recommends infants sleep on a firm, flat surface that is covered by a fitted sheet, without any other bedding or objects in the sleep environment to reduce the risk of sudden infant death syndrome (SIDS). A mattress that is firm is better than a softer mattress, she says.

illustration of crib mattress in crib showing importance of mattress firmness

If you want to ensure some extra durability and safety for the crib mattress, Witkin likes to recommend a mattress that is easy to clean, comes with a waterproof/machine-washable cover, is made with non-toxic and environmentally friendly material, and is flame-resistant.

It can also be beneficial to look for a crib mattress that offers breathability. A breathable mattress can help keep your baby cooler during warmer months, explains Witkin. Organic cotton and wool are two breathable materials to look for in a crib mattress.

Crib mattress vs. other mattress sizes

To give yourself some perspective, this section will break down the differences between crib mattresses and other mattress sizes that might be suitable for babies and children.

Toddler mattress vs. crib mattress

Even though toddlers are larger than babies, there are no perceivable differences between crib mattresses and toddler mattresses, according to Witkin. Many cribs actually convert to toddler beds and are designed to be used with the same mattress, she says.

Crib mattress vs. twin

A twin mattress measures 38 inches x 75 inches, making it a great deal larger than a crib mattress. You can think of it as the next step up, or the big kid bed, your toddler will eventually graduate to. Twin beds are also best for bunk beds, daybeds, or small spaces with solo sleepers.

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Crib mattress bedding sets and accessories

Once you’ve purchased a crib mattress, there are other things you’ll need to stock up on, like bedding sets and accessories.

  • Fitted sheet: “If your baby is sleeping in a crib or bassinet, you will need, at a minimum, a mattress and fitted sheet,” says Witkin. “I always recommend having at least two sheets so that when the inevitable diaper explosion occurs during the night, you’ll have another sheet available immediately.”
  • Mattress protector or pad: Since those “diaper explosions” are basically guaranteed, a waterproof mattress cover can be a lifesaver.
  • Wearable blanket/onesie: “As it is not safe for infants to sleep with loose blankets or covers, a wearable swaddle or sleep sack is key,” Witkin says. “Swaddles that have Velcro or zippers are an easy and convenient solution.”
  • Crib: You don’t need to focus on the frills when it comes to the crib itself. “At the end of the day, your baby needs a firm, flat surface that is free of objects in which to sleep,” says Witkin. “For some families, this may mean a crib and a mattress, and for others, that might mean a cardboard box. From a safety standpoint, either is acceptable!”

There are also items that you should never put in a crib when a baby goes to sleep.

“Babies’ cribs and sleep environments should be free of pillows, loose blankets, and stuffed animals,” advises Witkin. “Additionally, you should avoid overheating your baby with too many layers of clothing and a hat. In general, babies need one more layer of clothing than you do to be comfortable.”

While there should be nothing in the crib except for the baby, Witkin notes that the exception to this is a pacifier since it’s been associated with a decreased risk of SIDS. Avoid pacifiers that clip to clothes during sleep, though.

Crib mattress size FAQs

What’s the standard size of a crib mattress? What are the types of crib mattresses? Keep reading for answers to your most common questions about crib mattress dimensions.

What is the standard size of a crib mattress?

A standard crib mattress size is 28 inches x 52 inches.

Why are crib mattress dimensions important?

Crib mattress dimensions are important because you’ll want to avoid gaps between the mattress and crib, which could pose a safety hazard for the baby. Experts say there should be less than an inch between the mattress and the crib when the mattress is pushed up against one side.

Are all crib mattresses the same size?

Although there is a standard crib mattress size, there are other less popular sizes available as well. This includes the mini crib mattress, which measures 24 inches x 38 inches.

What are the types of crib mattresses?

Like mattresses geared toward adults, there are two main categories of crib mattresses: foam, which is made up of a blend of materials and doesn’t use metal springs, and innerspring, the most common type of mattress that relies upon a system of metal springs.

How firm should a crib mattress be?

A crib mattress should be pretty firm, according to experts. It’ll be safer for the baby than a soft mattress.

How big is a crib quilt?

Crib quilts are usually measured at 30 inches x 46 inches or 36 inches x 50 inches. They’re rectangle-shaped and are made to fit most crib mattresses.

When should a child be out of a crib?

“I typically recommend waiting until a child is at least three years old to transition to a toddler bed,” says Witkin. “Prior to this time, it is difficult from a developmental standpoint for children to understand the concept of staying in their bed.” The only exception to this is if your toddler is climbing out of the crib and there are safety concerns about falling, she adds.

Also, note that the AAP recommends placing an infant’s crib or sleep area in the same room as their caregiver for at least the first six months of age.

Additional mattress sizes

To learn more about other mattress sizes, check out our additional mattress size guides.

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