The Baby Mattress Firmness Test You Need to Know About

How Firm Should a Crib Mattress Be?

When it comes to crib mattresses, you really can’t compare what’s comfortable for an adult with what’s comfortable (and safe) for a baby. And when it comes to babies, the firmer the crib mattress, the better.

A firm crib mattress is necessary to support a babies skeleton, ensure the baby’s safety (and prevent suffocation), and more. To learn why a crib mattress is important and how to tell if a crib mattress is firm enough, keep reading.

Yes, a Firm Crib Mattress Really is Necessary for Your Baby

If you’ve spent any time reading crib mattress reviews online, you’ve probably come across one of the most common criticisms from moms, dads, grandmas and grandpas in charge of buying a baby crib mattress:

Hard as a rock! I know babies should have a firm crib mattress, but it shouldn’t feel like sleeping on a rock!

If I wanted a crib mattress this hard, I would let my baby sleep on our wooden floor.

And, inevitably…

It was just way too firm. There’s no way I would sleep on this mattress. I can’t imagine my baby sleeping on it. It just doesn’t seem comfortable.

Honestly, we get where these parents and grandparents are coming from.

You want the best for your baby. And that includes making them comfy and cozy when they head off to dreamland.

All parents want their babies to sleep well and breeze through sleep regressions and transitions.

It seems like common sense that a too-firm mattress would be uncomfortable for the baby, and would lead to a poorer quality sleep, right?

(For the record, I hear the same complaints about pack n plays and travel cribs, too, which is why many parents think they need to make their pack and play more comfy – don’t do this, as it’s not safe!).

Looking for a firm, non-toxic crib mattress and don’t have a lot of time to waste? We got you! Here are our top picks for a firm baby crib mattress:


Here’s the thing. Babies are different from adults. Adults (and even bigger kids and teens) can do loads of things babies can’t – or shouldn’t – do. And that includes sleeping on a soft mattress.

When it comes to crib mattresses, you really can’t compare what’s comfortable for an adult with what’s comfortable (and safe) for a baby.

They’re just plain different.

And when it comes to babies, the firmer the crib mattress, the better.

This is true for sleeping in a crib, a mini crib, a bassinet, a pack n play, and even a Montessori-style floor bed. And, frankly, it also keeps them a bit safer when they start to get adventurous by either standing in their crib, or trying to climb out.

Why A Firm Baby Mattress is an Absolute Necessity

Skeletal Support

From a developmental perspective, firm crib mattresses give babies the support their bones and skeletons need as they develop and grow.

Whereas adults have 206 bones, babies have around 300! Between birth and the time the baby turns 25, some of their bones fuse together, which is why adults have less bones than babies.  

Whereas adults have 206 bones, babies have around 300! This is one of the reasons a firm crib mattress is so important for babies. Click to Tweet

Not only do babies have more bones than adults, they also have much softer bones. In fact, some bones in a baby’s body aren’t actually made of bone just yet. Instead, they’re made entirely (or partly) of soft, flexible cartilage. As the baby grows, bone replaces the cartilage.

A baby’s skeleton is very different from an adult’s, and it requires more support. Babies’ spines need more support than adults’ spines. And babies’ bones need more support than adults bones.

Firm crib mattresses offer that support, whereas soft crib mattresses do not.


Firm crib mattresses are also essential to a baby’s safety. Soft crib mattresses are come with a higher risk of SIDS than average or firm crib mattresses.

The same goes for soft crib mattresses and suffocation risk.

If a baby is put to sleep on their stomach or rolls onto their stomach during sleep, soft mattresses can conform to the baby’s face. This increases the risk of suffocation.

Soft mattresses may also be dangerous within the context of the so-called rebreathing theory. According to this theory, soft bedding and mattresses increase the risk of a baby’s exhaled breath getting trapped around its face, causing the baby to re-breath its own exhaled breath (carbon dioxide).

It’s important to note there “are no physiologic data from infants who died” to support the rebreathing theory to date.

However, since it’s so easy to choose a firm crib mattress instead of a soft one, why wouldn’t you?

If you’re particularly concerned, you might consider whether a breathable crib mattress is right for your family.

Finally, soft mattresses can have malleable sides and corners. This can allow for gaps to be created between the crib edge and the mattress edge, and it’s possible babies can get stuck in these gaps.

Related Reading

How Much is a Crib Mattress? A Guide for New Parents

Firm Crib Mattresses: The Experts Agree Firmer is Better

If you need more evidence to convince a partner, grandparent, or co-parent that a firm bassinet mattress and/or crib mattress is best for your baby, take a look at what some of the experts say:

  • The National Institute of Child Health and Human Development: “Never place baby to sleep on soft surfaces…. These surfaces can be very dangerous for babies.”
  • The Center for Disease Control: “Use a firm, flat sleep surface, such as a mattress in a safety-approved crib covered by a fitted sheet.
  • (a not-for-profit organization): “A firm mattress covered with a tight-fitting crib sheet is all you need to make your baby sleep like a baby.”
  • American Academy of Pediatrics: “A firm surface is a hard surface; it should not indent when the baby is lying on it.”
  • American Academy of Pediatrics (again): “The American Academy of Pediatrics recommends a safe sleep environment that can reduce the risk of all sleep-related infant deaths. Recommendations for a safe sleep environment include supine positioning, the use of a firm sleep surface, room-sharing without bed-sharing, and the avoidance of soft bedding and overheating. Additional recommendations for SIDS reduction include the avoidance of exposure to smoke, alcohol, and illicit drugs; breastfeeding; routine immunization; and use of a pacifier.”
  • Healthy Families BC (a provincial government organization): The mattress should be firm. If it’s worn or has a tear, it’s dangerous. Don’t use it.
  • Health Canada: Check that the mattress is firm. Mattresses that are too soft or worn down in any area could create a gap where a baby’s face could become stuck, causing them to suffocate.
  • The Canadian Pediatric Society: Use a firm, flat surface for sleep. Waterbeds, air mattresses, pillows, couches/sofas or soft materials are not safe sleep surfaces for babies. Babies can turn onto their side or stomach and bury their face in these soft materials, not getting enough air to breathe.
  • Dr. Shavon Artis Dickerson, Head of the Eunice Kennedy Shriver National Institute of Child Health and Human Development’s Safe to Sleep campaign: “…you want to make sure that the baby is on a firm sleep mattress because if the baby rolls over, they could roll over onto a soft mattress where they actually—their face or nose becomes buried in the mattress.”

There’s virtually no professional organization operating in child health and safety that doesn’t argue the case for a firm crib mattress.

The experts have weighed in, and they’ve made an overwhelming case in support of buying a firm crib mattress for your baby.

How to Tell if a Crib Mattress is Firm Enough? The Baby Mattress Firmness Test You Need to Know About

When shopping for a firm crib mattress, we recommend you start with what we call the FIRMS checklist:

F – Firm and Flat: Look for a crib mattress with a firm, flat surface. There shouldn’t be any peaks or valleys on the mattress.

I – Indentation Resistant: When a crib mattress arrives, you should test it’s resistance to indentations. Simply press the mattress in the middle, and again around the mattress edges. If the mattress is firm enough for your baby, it will snap back right away, rather than conforming to your hand or fingers.

R – Recall List: Before you let your baby sleep on a new crib mattress, double check it’s not on the recall list. Americans can check for baby product recalls here, and Canadians can check here. We’d recommend you check both lists, just in case.

M – Mattress Edges and Corners: Firm crib mattresses will have strong and stable edges and corners that can’t be pushed inwards to create a gap between the crib edge and mattress. Double check the mattress in your crib to ensure there’s no way to create large gaps.

S – Soft Isn’t Safe: This one isn’t so much a checklist as a reminder. If the crib mattress seem like it would be comfortable for you, it’s probably too soft for your baby. When it comes to baby mattresses, firmer is always better, so don’t be afraid to look for an extra firm crib mattress.

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