Just like cribs, crib mattresses come in different sizes. Looking at a mattress, you wouldn’t know, so we’re here to answer the question “Are all crib mattresses the same size?”. We’ll also explain why crib mattress size matters!

How Big is a Crib Mattress?

There are so many styles of cribs on the market - modern, traditional, convertible, designer, bare-bones, take your pick! No matter the design, any crib manufactured and sold in North America, must be built to fit a full size crib mattress. So, what are the dimensions of a crib mattress and how long is a crib mattress? 

All North American crib mattresses must measure between 51 ⅝ to 53 inches in length and 27 ¼ to 28 inches in width (thickness can range from 4 to 6 inches).

Why the Variance in Size?

There are three main reasons: 

Fit: If you can place more than two fingers between the mattress and the crib, the mattress is too small. Some mattress brands use smaller dimensions to cut costs.

Firmness: Foam that’s too soft or bouncy inner springs can contribute to a mattress with too much “give”, leaving gaps around the edges. This poses a safety hazard if tiny hands or feet, or even worse, baby’s face, gets caught between the mattress and crib rails.

Materials: What your crib mattress is made of plays a major part when it comes to how a mattress will fit in the base of the crib, like the aforementioned soft foam or inner springs.

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