Crib Mattress Buying Guide: Types, Firmness & Certifications

When your little one turns two years old, they will have spent roughly half of their life sleeping in their crib. Thus, it is essential to thoroughly contemplate the suitable mattress for their crib.

It’s easy to assume that your baby’s bedding ought to be as soft as a cloud, but for the sake of your baby’s health, the exact opposite is true.

Why should baby mattress be firm?

It’s important that a baby mattress is firm and flat as a soft bedding surface can sag under their weight, causing indentations that may pose a suffocation hazard and increase the risk of SIDS (sudden infant death syndrome). Opt for high-quality organic or spring crib mattresses over foam styles.

The firmness of your baby’s crib mattress (or adult mattress if you’re trying out co-sleeping) is just one of many key safety features to consider.

You’ll also want one that has been tested for low chemical emissions and indoor air quality and one that is the right fit for their crib.

In this buyer’s guide, we’ll explain these key aspects and answer your crib mattress safety concerns.

Baby Mattress Safety

As your little one spends most of their early life in bed, choosing the best possible mattress is important.

There’s a lot to consider when it comes to mattress safety from the appropriate firmness and material to the size and proper certifications.

Let’s find out what you need to know.

Foam vs. Spring Crib Mattress

Crib mattresses often have a foam or spring (coiled) design.

The former is typically the low-cost option, and these are made from a single layer of thick foam (3-4 inches thick), often with a waterproof fabric cover that can be easily removed and washed.

Foam crib mattresses can make babies feel clammy during hot weather, and they are not as firm as spring mattresses since the baby’s weight can eventually create an indentation in the material.

Memory foam crib mattresses are not recommended for this reason.

Spring mattresses are a little more expensive and are made of coiled springs aligned next to each other inside the mattress or enclosed in individual fabric compartments in the case of pocket-spring crib mattresses (similar to adult mattresses).

While both types of spring mattresses are firm and hold their shape well compared to foam, the springs may be felt through the mattress surface, so a mattress topper may be necessary for your baby’s comfort.

Organic vs. Synthetic Materials

Organic crib mattresses are stuffed with natural fibers such as coir (coconut fibers) and are often coated in latex rubber.

This creates a durable, firm mattress that doesn’t sag, though organic mattresses are quite pricey.

Traditional synthetic foam and spring crib mattresses may be low-cost options, but there can be a possibility that these are made with chemicals and fire retardant materials, particularly if they are not certified (more on certification later).

Organic mattresses tend to come with a number of different certifications, so these can be a worthwhile investment.

Mattress Certifications

Crib mattresses are regulated for their standards on things like flammability, chemical production, and indoor air quality.

If you’re considering investing in an organic crib mattress, Baby List recommends looking for one with a GOTS (global organic textile standard) certification.

This means it has to contain at least 70% certified-organic fibers or as much as 95% if the mattress is labeled as GOTS-certified organic.

For conventional crib mattress types, be sure to look for a GREENGUARD Gold certification as this means the entire crib and its components have been tested and lab-approved for indoor air quality and low emissions.

For foam crib mattresses in particular, greater safety can be found with a CertiPUR-US Certified foams certification on the packaging as this will have been tested rigorously for durability, chemical content, and indoor air quality.

A newborn sleeping on a crib mattress topped with sheets decorated with anchors.

Firmness of Mattress

While firm may not sound comfortable for your baby, a crib mattress should always be firm over soft.

This is to ensure it won’t sag or mold into your baby’s shape, particularly at your baby’s head as sinking into the mattress material is a SIDS (sudden infant death syndrome) hazard due to the increased risk of suffocation.

Mattresses should be no thinner than 3 inches thick to provide the right firmness, though 4 inches is better for support, especially if you are buying a foam crib mattress.

Fits Snugly in Crib

The right mattress will fit snugly into their crib with virtually no gaps (a gap of 1.5 inches around the mattress at most).

Using too small a mattress can risk your child becoming trapped between the mattress and crib.

It helps to purchase both a crib and crib mattress in-store to test out the snug fit for yourself.

If your crib is not of a standard size, some companies will make a custom-fit mattress for extra peace of mind.


Babies breathe a lot more than we do, so it’s important that their mattress has a good breathability score.

Opt for ones made from hypoallergenic materials to help keep your little one’s allergies at bay, and don’t forget about mattress certifications that guarantee indoor air-quality testing.

Crib Mattress Pad

To keep your baby’s crib mattress in good condition for as long as possible, it’s wise to get a pad to fit over the crib mattress.

This waterproof fabric topper protects the mattress against any nighttime leaks, milk/formula spills, moisture, and mold.

Without a mattress pad for the crib, bacteria can seep into the mattress, leaving behind germs that could make your little one sick.

Crib Sheets

Crib sheets add the finishing touch to your baby’s mattress, providing a soft layer for sleep and a cute pattern or color scheme that can tie in nicely with their nursery décor.

It’s wise to have at least three crib sheets on hand at all times for laundry cycles.

Also, note that it should fit snugly over the crib mattress (There are standard crib sheets and mini crib sheets for mini cribs, so make sure you have the right size).

How To Tell if Crib Mattress Is Firm Enough

According to the organic mattress team at Naturepedic, a good way to test that your baby’s crib mattress has the right firmness is to press on the mattress at the center and the corners — it should snap back quickly and shouldn’t take on the mold of your hand.

How To Tell if Mattress Is Firm Enough for Co-Sleeping?

Your mattress should be firm enough for sleeping with your little one if you can lie close to them and they don’t roll or turn over.

Your mattress also shouldn’t create a mold or indentation of your body when you lie down.

A high-quality spring mattress is preferable over a foam one, and as ever, pay close attention to the mattress certification for extra co-sleeping safety.

At What Age Can Babies Sleep on Soft Mattress?

On the advice of the American Academy of Pediatrics (AAP) safe sleep guidelines, babies should not be sleeping on a soft mattress until at least 12 months old.

Before this age, there should be nothing in their crib besides a mattress, fitted crib sheet, and possibly a mattress pad.

To play it safe, any soft furnishings such as blankets, cuddly toys, stuffed animals, or pillows/cushions should not be introduced until after 12 months when they may begin moving into a softer toddler bed.

Toddler Mattress vs. Crib Mattress

The main difference between the two is that a toddler mattress can be much softer than a crib mattress if the child prefers.

This is because your toddler can now sleep in various positions and has full control of his/her head as they sleep, so they are no longer at risk for suffocation.

Regarding size difference, many toddler mattresses can have similar if not the same dimensions as crib mattresses (approximately 27.25” W x 51.625” L).

Helpfully, some crib mattresses can be flipped with one firm side and one soft side, making the transition to a toddler bed much easier.

Related Questions:

How Often Should You Change Crib Sheets?

It’s recommended that you change your baby’s crib sheets at least once a week, changing twice a week or more if they are soiled or stained frequently, i.e., if your baby drools a lot or pees/poops the bed.

Sheets can also collect bacteria from diapers, milk spills, and other people.

Are Bumper Pads Safe for Baby Cribs?

Bumper pads are best avoided in your baby’s crib.

According to the American Academy of Pediatrics (AAP) sleep-safe guidelines in 2011: “There is no evidence that bumper pads prevent injuries, and there is a potential risk of suffocation, strangulation, or entrapment.”

Final Thoughts

We hope you have found this guide helpful in choosing the safest crib mattress for your little one.

When shopping for their mattress, check first and foremost for one that is firm and the right size for their crib.

The ideal crib mattress should also come with a certification to denote quality testing and be made of a breathable hypoallergenic material to help your baby drift off into safe and comfortable slumber.