The Ultimate Guide to Crib Mattress Heights

Ultimate Guide to Crib Mattress Heights

As new parents, a lot of questions arise revolving many different areas. One common thing that many parents worry about is what height their baby’s crib mattress should be at. Is it supposed to be adjusted throughout their growth, and if so, how much should you adjust? 

The following guide will help you learn how to provide a safe setting for your child in a crib as they grow, including information about the correct crib mattress heights according to different situations. 

Why Should You Change the Crib Mattress Height?

There’s a good reason why many crib mattresses can be adjusted: your baby’s safety, as they sleep or are in their crib, partially depends on how low or high their mattress is. Using a non-adjustable crib or not changing the crib mattress height as your child grows can put them at risk of sustaining injuries that can easily be avoided. 

For example, if the crib mattress is too high, if your baby happens to figure out a way to climb out or over the railing, they could become seriously hurt from falling from a higher height. 

What If I Don’t Have an Adjustable Crib?

While most cribs today can be adjusted and will have from three to five settings to do so, some are not equipped to adjust. If you don’t have the means to purchase an adjustable crib, don’t worry. An alternative you can use is to layer up mattresses; average crib mattresses are usually thin, so you can always add or remove mattresses to heighten or lower it. 

However, we highly recommend investing in an adjustable crib since many can eventually convert into a toddler bed when necessary for more long-term use. 

What Should Be the Starting Crib Mattress Height for a Baby?

When your baby is a newborn, you should use the safest, highest setting possible. Babies are the least active at this point; while they may squirm a bit, they won’t dance, jump, or climb, risking the possibility of falling out. 

In addition, setting the crib at the highest height while they’re a newborn makes things easier for you; you won’t have to bend over as far and put a strain on your back if you ever want to pick them up. Also, if you had a C-section, you can avoid the discomfort of bending over the crib’s railing. 

Babies around five months old can usually sit up at this point and be a little more active; this is when you can begin to lower your crib’s mattress to a mid-height setting. And, as they get older and taller, you’ll want to gradually lower the mattress even more. (In the case of layering mattresses, simply remove one more from the stack over time; more on this later in the article.)

Adjusting the Crib Mattress Height as Your Child Grows

There are a few milestones to look out for with your child that can help you determine when it’s time to start lowering your mattress:

Sitting Up (5 Months Old)

As mentioned earlier, once your baby can sit up, or around the age of five months, you should start to lower the mattress to a middle setting. If your baby is already able to sit up, they will be able to pull themselves over the railing or tumble over. This is very dangerous and is, unfortunately, a common accident that happens

Standing Up (8 Months Old)

Once your child learns how to stand, you should lower the crib mattress to the lowest setting possible. A child usually learns how to stand at around eight months, but this varies. Make sure to observe your baby in their crib to see how they move around and if they can pull themselves up to a standing position. The second you notice they can do that, lower the setting, even if they are under eight months old. 

Otherwise, if you notice that they’re more mobile than they were before, make sure the mattress is lowered to avoid any accidents. 

Is it Safe to Lower a Crib Mattress to the Floor?

It is definitely safe to lower a crib mattress to the floor. This is an especially great idea for toddlers who can stand up in the crib. The less space there is between the child and the top of the railing, the safer it is. If your child can’t reach the railing or if they can, only a little bit, then there is no way that they can fall over it or climb out of the crib. They don’t have the upper body strength to do so. 

Changing Crib Mattress Heights with Non-Adjustable Cribs

If you happen to have a crib that isn’t adjustable, you can change the height of stacked mattresses by adding more or removing them. Baby mattresses, the ones used in cribs, usually are on the thinner side, so you can stack two or three of them together if you want the mattress to be high up for a newborn. As the baby grows, you can remove them one by one until it is safe for their height and actions, as mentioned above. 

You won’t be able to do this with thicker mattresses because the height of the crib isn’t long enough, but the following mattresses would work:

What If My Child Can Lean Over the Crib Railing?

Once your toddler reaches the railing, you could turn their crib into a toddler bed. This usually happens once your child is around thirty-five inches tall or two years old. Most adjustable cribs have the option to convert into a toddler bed. 

Keep in mind that toddler beds have an open side. With that said, ensure that your child’s room is baby-proofed so they can’t hurt themselves if they wake up at night and walk around. There should be safety covers on doorknobs so that they can’t open their door and walk out. Also, make sure that there are baby gates on all of the staircases just in case they wander out of their room. 


When it comes to adjusting the crib mattress height for your baby, remember that you’ll need to change it as your child grows. This will ensure your baby remains safe throughout each stage of their life, from sitting up for the first time to learning how to stand.  

We know that your child’s safety is the number one concern on your mind. With all of the anxieties a parent experiences, you would expect cribs to be the least of your worries. Sadly, that isn’t the case, but as long as you remember the tips above, you can rest easy knowing that your crib is a safe haven for your child. 


Hi there! I’m Alex, the one behind this website. I ran and operated a Local Furniture Store in Southern California. The store opened in 2010, during the “Great Recession,” It is still thriving today; however, I have dedicated my time to helping our online customer base. My primary focus is to help you with all your furniture & mattress questions.

Related Posts