Skip to Content

Top 8 Questions You Need to Ask Before Using a Crib Mattress in a Toddler Bed 

Top 8 Questions You Need to Ask Before Using a Crib Mattress in a Toddler Bed 

Is your crib-bound toddler making escape plans, or testing the strength (and height) of the crib bars?

Whether you’ve got an especially adventurous toddler or your little one is simply not so little anymore, you might be wondering the best when and how to make the switch from crib to toddler bed.

Keep reading as we delve into the top 8 questions you need to ask before using a crib mattress in a toddler bed, including useful facts and best practices for this milestone.

Questions to Ask Before Using a Crib Mattress in a Toddler Bed Pint

1. Does a crib mattress fit a toddler bed?

Does a crib mattress fit a toddler bed? It depends on whether your existing crib converts to a toddler bed, or if you’re buying a completely new toddler bed.

If your baby’s crib does convert to a toddler bed, then yes, that same mattress will fit. So what size mattress goes in a crib? It may depend on the manufacturer, but standard crib mattresses are generally 27 ¼ in x 51 ⅝ in. 

convertible crib
This is an example of a convertible crib, which transitions from a crib to a toddler bed by swapping out one side of the crib frame.

Many forward-looking parents buy a crib with the toddler years in mind. If that’s you, first, congratulate yourself on saving some money! You’ve done the hardest part, too; you’ve filtered through all the options and actually made a decision. (Too much choice can be overwhelming, don’t you think?)

All that’s left is to find the allen key and spare parts and, voila, your baby’s crib is now a toddler bed, almost as quickly as the baby became a toddler.

Some parents may want to buy a new mattress for their toddler when they do make this transition. Perhaps your baby’s mattress has endured a few too many leaks without a waterproof cover. Infant mattresses tend to be more firm for safety reasons, too, so a softer mattress might be more comfortable for your toddler. 

Maybe you’re not worried about whether or not a mattress fits the bedframe. They can’t be all that different, can they?

Maybe the better question is:

2. Is a crib mattress the same size as a toddler mattress?

If your crib doesn’t convert and you’re buying a completely new toddler bed, it’s true that you may need a different mattress size. Infant mattresses and toddler mattresses are not always the same size or firmness level, just as cribs are not necessarily the same size as toddler beds.

So, what size mattress does a toddler bed use?

It depends on the manufacturer, but toddler bed mattresses can range from  27 ¼–31 inches wide and 51 ⅝–71 inches long. But because toddler beds often come with a mattress, you shouldn’t have to hunt around for the correct size.

Always read the product details to find out the exact measurements.

This brings us to a related question: sheets! 

3. Do crib sheets fit toddler beds?

Sheets are stretchy and flexible, right? Good news, then: some crib sheets can actually fit pretty snugly on a toddler bed mattress. The thing is, not all crib sheets will fit perfectly because of that slightly different dimensions issue.

crib sheets

To make sure you get the best fit, it’s a good idea to check the dimensions of your toddler bed mattress and compare them to the measurements of the crib sheet. Keep in mind that it’s not just the length and width you want to look at; the depth (thickness) of the mattress plays a part, too.

It’s possible your crib and toddler bed have the same length and width, but if the toddler bed mattress is significantly thicker, it’ll make it harder for crib sheets to fit the toddler bed.

If trying to fit a too-small sheet involves you nearly throwing your back out, it might be best to look for sheets that are specifically designed for toddler beds.

Besides, when it involves kids, it’s never a bad idea to have extra sheets.

Related: Crib Weight Limits: Can I Get In My Baby’s Crib?

4. How do you convert a crib to a toddler bed?

First, the best question to ask yourself is, do you have a convertible crib?

Convertible cribs often come with a guard rail, so when you take the long side off the crib, the guard rail goes in its place. This helps keep roly-poly toddlers in bed and gives them that sense of containment that some kids like.

Companies do sell guard rails individually, though, so it may be possible to simply take the long side off your child’s crib, and then fit a guard rail you’ve purchased separately. Read the instructions that came with your crib to check if this is a safe option.

Most cribs are held together with bolts, so you’ll probably only need the right-sized allen key.

You may need a second person to hold the side in place while you loosen bolts, or to hold the guard rail in place while the other person tightens bolts.

Converting a crib to a toddler bed should be easier and more straightforward than, say, assembling my sons’ bunkbed (which took three men two hours).

5. Do you need a new mattress for a toddler bed?

As mentioned before, new toddler beds should come with a mattress. But what if your toddler bed isn’t new? 

If you’re like me, you might be the type of person always on the hunt for a bargain. (I may be addicted to scrolling through Facebook Marketplace.)

Maybe you’ve found a second-hand toddler bed and now need a new mattress. 

Before you commit to a certain bed, measure the bed carefully (or get exact measurements from the seller) to find out what size mattress you need. For safety reasons, it’s best that there’s no less than a one-inch gap between the mattress and bedframe.

Children can become wedged between too large a gap, and that can be dangerous.

helix kids mattress

Note: our family has the Helix kid’s mattress, and it’s incredible! I’m not an affiliate with the brand and this mention isn’t sponsored in any way. We genuinely love this mattress.

6. Can you use an infant mattress for a toddler?

Maybe your budget is a little tight, and you have a perfectly good infant mattress that still fits your toddler. As long as you’re converting the crib to a toddler bed (and the mattress still fits the bedframe), you can use an infant mattress for a toddler!

Just keep in mind that some infant mattresses tend to be more firm, which might end up not being as comfortable for your growing little one. 

The newton infant mattress is very firm
The Newton infant mattress is very firm.

It may make sense to hang on to an infant mattress, especially if it’s in good shape and if you’re not done growing your family.

Some experts recommend getting a new mattress for every child, but if you’ve kept a waterproof cover on it and it’s still firm enough to support an infant – well, I know that families can’t always get brand-new stuff for subsequent kids. (Fellow middle children, I stand with you in solidarity.)

7. What age do kids outgrow a crib mattress?

As a new parent, I often felt like there were strict right and wrongs when it came to milestones–and I got anxious about following the “rules.” 

Sure, there are guidelines, but so many things depend on your individual child.

So if you’re asking, “What age do you convert a crib to a toddler bed?” I’d say this question fits that “gray area” category.

Kids typically outgrow crib mattresses between ages 2 and 3, but there are many factors at play here.

  • Is your child tall for her age? She might be able to climb out of the crib earlier than another child, or she may need more space to stretch.
  • How advanced are your child’s motor skills?
  • Is he shorter–but a good climber?

Honestly, a lot of this even comes down to personality:

  • Adventurous vs. timid
  • Rule-breaker vs. rule follower
  • Sleep lover vs. sleep-allergic

If your child is consistently trying to climb out of their crib, it might be time to make the switch to a toddler bed simply for safety reasons.

Some kids can’t handle so much freedom all at once; I have a friend who tried the big-boy bed for her son, but it was so disastrous that she put him back in a crib for a little while longer.

Consider your child’s individual growth and needs, as some kids may outgrow their crib mattress earlier or later than others.

8. Is a twin mattress the same size as a crib mattress?

So far, we’ve been talking about crib mattresses vs. toddler mattresses. It’s time to add a third option into the mix: the twin mattress.

Sadly, a crib mattress is not the same size as a twin mattress, and it won’t fit a twin bed frame.

While your standard crib mattress usually measures 27 ¼ in x 51 ⅝ in, a twin mattress is about 38 in x 75 in. Twin mattresses are a good size for both kids and adults.

Wondering about toddler mattress size vs twin bed size? It won’t surprise you then that toddler mattresses also do not fit twin beds. But, a twin bed is still a viable option for a toddler!

We recently got twin bunk beds for my boys (ages six and three). My three-year-old had already been in a toddler bed, though, so he was used to the newfound freedom and had already (mostly) learned to stay in bed at bedtime. He would’ve still fit in his toddler bed, but the twin size is great for him as he grows.

So, if you want to skip the toddler bed altogether and go straight for the twin, I’d say go for it. That makes it easier if you ever have guests coming to stay, as they can easily use the kids’ room. 


Transitioning to a toddler bed is a big milestone, and you’re right to ask questions!

If you’re making the switch from crib to toddler bed, keep these things in mind:

  • A crib mattress is not necessarily the same size as a toddler bed mattress unless you’re converting your crib to a toddler bed. You may need new sheets, too!
  • Kids typically outgrow a crib between age 2–3 depending on their size, motor skills, and sense of adventure.
  • A twin mattress is larger than a crib or toddler mattress.
  • You can use an infant mattress for a toddler, but it may not be as comfortable for your little one.
  • Convertible cribs come with a separate guard rail; you’ll typically just need an allen key to convert the crib (possibly an extra set of hands).
  • A toddler bed usually comes with its own, right-sized mattress.
  • When it comes to the right size bed or right age to make a change, not everything is right and wrong; decide what’s best for your own child.

If your toddler is the adventurous type and relishes his newfound freedom at bedtime, it’s possible you’ll need all the tips and tricks for keeping your free-ranging toddler in bed – but that’s for another blog post.