A crib is the piece of furniture that your little one will use the most for the next few years. Crib mattresses are government-regulated to ensure a safe environment for your little one, so it is important to select a mattress within the right dimensions. With various crib styles and shapes, there are different sizes of crib mattresses. To help determine the best – and safest – sleeping experience for your baby (and you, by extension!), follow our guide to pick the correct crib mattress size.

Why Crib Mattress Size Matters
How to Measure a Crib for a Mattress
Types of Crib Mattress Sizes

Why Crib Mattress Size Matters

The right crib mattress size ensures the safety of your little one because it fits snugly against the sides of the crib and prevents gaps. This keeps your child from becoming wedged between the crib and the mattress. Therefore, you can sleep soundly knowing your baby can sleep and roll around safely with the help of the right mattress size. This idea also applies to different crib mattress shapes, because a compatible mattress shape prevents large gaps around the edges of the crib. You should always match your crib mattress to the frame’s recommendation. For example, pairing a rectangular crib with a mini crib mattress or oval crib mattress creates significant gaps in the corners and sides of the crib, while the recommended standard crib mattress fills in all the gaps for a safe sleeping space.

Tip!

Learn more about crib safety features and guidelines in our Baby Crib Buying Guide.

How to Measure a Crib for a Mattress

There are a few key steps to take to determine the right mattress size for your crib.

1. Review Your Crib's Product Manual

Start here if you have your crib's product manual on-hand to reference. Most crib manuals should list compatible mattress sizes and types so you don't even need to take your own measurements. You can also determine compatible mattress sizes for your crib by going to the crib's product page and taking a look at the “You Might Also Need” section below the Add to Cart button.

2. Measure the Crib's Interior Length & Width

If you don’t have your product manual, or can't find compatible mattress information, don't worry! The crib mattress measurement process is quick and simple. Take a tape measure and place it on the inside of the crib. Measure across the interior of the long side of the crib to the other side to determine the correct mattress width. Then measure from the interior of the short panel on the end of the crib to the one directly across from it. This should measure the length of the crib and the length of the compatible mattress size.

3. Subtract a Half Inch From Your Measurements

As a general rule of thumb, there shouldn't be more than 1 inch of space between the crib and the crib mattress or more than two finger-lengths. Subtract a half inch from the total length and width of the crib to determine a good mattress size. This helps ensure that you can easily lift and lower the mattress into the crib, while also making sure the mattress fits snugly against all sides of the crib.

Tip!

Don't have a crib just yet? Check out our crib dimensions guide to help determine the right size for your nursery.

Types of Crib Mattress Sizes

The right crib mattress size should fit snugly inside a crib and accommodate the crib's shape to prevent gaps between the sides of the crib and the mattress edges. Check out these crib mattress shapes or skip to size options to get started:

Crib mattresses typically fit into one of two shape categories:

• Rectangular/Square: Rectangular crib mattresses pair with standard cribs and other crib sizes that have a rectangular frame. Mini cribs typically have smaller rectangular or square-shaped mattresses.

• Round/Oval: Round or oval crib mattresses usually pair with bassinets or cradles and have cushioned sides to keep newborns safe and secure as they sleep. However, you can find standard round crib mattresses to pair with round-shaped crib designs.

With crib mattress shapes in mind, check out these different sizes of crib mattresses:

Standard Crib Mattress Size

The standard crib mattress size is 52" L x 27" W. The mattress is typically 5" – 6" thick and should not be thicker than 6". They are designed to fit snugly inside USA-standard full cribs, which have dimensions averaging within 5/8" of 52" L x 28" W. There should be no gaps larger than two fingers wide between the mattress and the crib.

Mini Crib Mattress Size

Mini or portable cribs are more cost-conscious and work well in tight spaces. The standard mattress size for a mini crib is 38" L x 24" W. The thickness tends to be lower, around 3" – 4" high and no higher than 5". Just like a standard crib, the gaps between the crib mattress and the sides of the crib should be no more than two fingers wide.

Cradle Crib Mattress Size

Cradles can vary in size but standard cradles can accommodate a mattress that measures 36" L x 18" W. These mattresses usually have 1½" thickness to maintain a firm, safe sleeping space for babies to sleep comfortably.

Bassinet & Moses Basket Crib Mattress Size

Bassinets are smaller than cradles and mini cribs, so they require smaller mattress sizes to fill out the space. Bassinet mattresses typically measure 30" to 33" L and 15" to 18" W. Like cradle mattresses, they have a thin but firm composition that is 1½" to 2" thick. This prevents the mattress from sinking with the weight of the baby and promotes healthy breathing while sleeping.

A Moses Basket crib is similar to a traditional bassinet in its round shape. However, it's more lightweight and portable. Moses Basket crib mattresses can have slight variations in size but typically range from 26" to 29" L and 13" to 16" W to fit inside a Moses Basket that is 29" to 32" L and 16" to 20" W. These types of mattresses are usually thin but firm and at least 1" tall to promote healthy breathing by keeping newborns from sinking into the mattress.

Tip!

Keep mattress weight in mind while shopping, since you will most likely be lifting or moving a crib mattress often to wipe it down or change the sheets. Mattresses that weigh more than 20 lbs. can be difficult to maneuver.

Start browsing for the best crib mattresses, now: