How to Choose a Crib Mattress

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One of the most delightful parts of expecting a child is putting together the nursery. It's also one of the most important. While the perfect paint shade and cutest bedding are nice, safe sleeping space is essential—and that starts with picking the best crib mattress for your baby.

While a mattress may just seem like, well, a mattress, there are specific safety considerations to keep in mind, as well as features that are worth looking (and budgeting) for.

Standard crib mattress size
Illustration by Joshua Seong, Verywell

Safety Standards

Because safety is central to choosing a crib and mattress, the dimensions of full-size cribs and mattresses have been standardized under federal regulations. That makes it easy to buy the two separately without worrying about fit.

The aim of these regulations is to prevent accidental head entrapment and suffocation between the mattress and the crib sides. The laws were enacted by the Consumer Product Safety Improvement Act of 2008 and officially went into effect in 2011.

The same rule doesn't apply to non-full-size cribs, however. Therefore, by law, these must be sold with the mattress included.

Remember that even if a mattress happens to fit inside the crib you choose, you should not use it unless it is a specifically designed crib mattress. Nor should you add a foam topper or other non-standard crib mattress cover to it.


A full-size crib mattress must be at least 27 1/4 inches wide, 51 1/4 inches long, and no more than six inches thick. At these dimensions, the standard crib mattress will fit safely in a full-size crib, which can have an interior width of between 27 3/8 inches and 28 5/8 inches, and an interior length of between 51 3/4 inches to 53 inches.

These dimensions and those of the mattress must be listed on both the retail carton and assembly instructions. Non-standard crib mattresses (say, for round or mini-cribs) can vary in size but must meet non-full-size crib standards, and all non-full-size cribs must be sold with mattress included.

When a mattress is placed in the center of the crib, there cannot be a gap of more than a half-inch at any point. If the mattress is pushed to one side, there cannot be a gap of more than an inch at any point. Again, this shouldn't be a worry for consumers, as non-standard cribs and mattresses are sold as sets. But it may be a concern if you are considering using an older, hand-me-down crib.

Note: The Consumer Product Safety Commission cautions against using a crib that is older than 10 years.

What to Look For

Since the federal regulations dictate an acceptable range in mattress dimensions, there can be a slight variation in the width, length, and depth. Before heading to the store or ordering a mattress online, check the label on your crib to make certain you purchase a mattress with the exact measurements needed.

Other things to consider:

  • Firmness: As a rule, firm mattresses are better for babies than overly soft ones. In fact, the firmer the better. Soft sleeping surfaces create a suffocation hazard for infants and increase the risk of sudden infant death syndrome (SIDS). One way to test firmness is to press on the mattress in the center and at the edges. When you release it, it should snap back immediately.
  • Non-toxic chemicals: A baby will spend more than half of their first year of life on this mattress, so making it as safe and healthy as possible is ideal. That means creating an environment that is free of toxic chemicals. If your budget allows, invest in a mattress that is as organic as possible. Look for GOTS (Global Organic Textile Standard) or GOLS (Global Organic Latex Standard) certification.
  • Depth and weight: Mattress depth doesn't necessarily translate to mattress firmness. Coil-spring mattresses tend to be on the thicker side—between 5 to 6 inches deep—whereas foam crib mattresses are closer to 4 to 6 inches deep. Foam mattresses tend to weigh less (with the exception of memory foam mattresses), which makes them easier to lift when you're changing sheets.
  • Duration of use: Some crib mattresses are reversible, with a firm side for babies and a slightly less firm, more cushioned side for toddlers. These are sometimes called "two-stage" mattresses, and they are clearly marked so you know which side to use when. (It is safe to flip the mattress from the baby side to the toddler side after baby's first birthday.)


While you don't want to cut corners when it comes to buying a crib mattress, you also don't have to blow your entire nursery budget either. A good quality mattress will cost between $90 and $200.

However, some special features come with a higher price tag. If you are looking for a mattress made of strictly organic materials or one that has an allergen-reducing cover, for example, you may need to spend more than $200.

If you are considering buying a used crib mattress to save money, you may very well find one that is suitable and up-to-standard. But confirming that is quite difficult, considering that it may be hard to determine if it was stored properly or was ever soiled. If at all possible, buying new is best.

Mattress Covers

Many crib mattresses come with a cover to help protect your investment from diaper accidents and other spills. They can also be purchased separately. Since this is the surface closest to baby (only a thin fitted sheet separates baby from this cover), look for one that does not have toxic chemicals, such as the organic, waterproof mattress protectors from Sleep & Beyond or Naturepedic. You may want a cover that offers:

  • Waterproofing (again, look for a chemical-free option)
  • Breathability (to keep baby cooler and more comfortable)
  • A hypoallergenic barrier (to keep allergens out)

Regardless of the features it offers, check to see if the cover's seams appear sturdy. Plastic seams can have sharp edges, so you will want to avoid those. Check fabric seams to make sure they are not stretched/strained and liable to rip.

Two Is Better Than One

Many parents appreciate have two mattress covers handy—one to put on the crib and one extra, just in case of accidents.

Replacing a Crib Mattress

If you need to replace the mattress in your crib, always check the warning label on the crib for the correct dimensions. If you don't see a label, it may be that the crib is older or has been modified. If in doubt, replace the crib entirely.

If you buy a mattress and find it doesn't fit correctly, return it immediately and get another one that does. Never try to make do by shoring up the edges with fabric or foam. Anything other than a snug fit is a safety hazard.

In this regard, while online shopping may be convenient, you may be better served shopping for mattresses at a brick-and-mortar store. You can then do a proper check of dimensions and firmness before making a purchase.

5 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. United States Consumer Product Safety Commission. Full-Size Baby Cribs Business Guidance & Small Entity Compliance Guide.

  2. Federal Register. Safety Standards for Full-Size Baby Cribs and Non-Full-Size Baby Cribs; Final Rule.

  3. United States Consumer Product Safety Commission. Non-Full-Size Baby Cribs Business Guidance & Small Entity Compliance Guide.

  4. United States Consumer Product Safety Commission. Safe to Sleep® - Crib Information Center.

  5. Consumer Reports. Crib Mattress Buying Guide.

Additional Reading

By Jennifer White
Jennifer White has authored parenting books and has worked in childcare and education fields for over 15 years.