What Size is a Crib Mattress?

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Preparing for a new baby can be overwhelming, but creating a safe and comfortable sleeping environment is a top priority. One of the most important decisions you’ll make is choosing the right size crib mattress. It’s not just about looks – the size of the mattress is crucial for your baby’s safety and well-being. That’s why there are established safety standards for crib mattress dimensions.

In this article, we’ll explore the different sizes available, as well as the guidelines you should follow when choosing a crib mattress. Our goal is to make sure you have all the information you need to make an informed decision and create a cozy haven for your little one. So let’s get started and learn why selecting the right crib mattress size is so important for your baby.

What are the Standard Dimensions of a Crib Mattress?

The standard dimensions of a crib mattress typically measure 27 1/4 inches in width and 51 5/8 inches in length. This standardized size is a common reference point for most cribs, providing a consistent and secure fit. It ensures parents have a reliable guide when selecting a mattress for their baby’s crib.

Related: Bed Sizes & Dimensions Guide

What is the difference between standard and non-standard mattress sizes?

While the standard dimensions are widely accepted, there are variations in crib sizes, leading to standard and non-standard mattress sizes. Here’s a breakdown of the key differences:

Standard Crib Mattress Sizes:

Standard crib mattress sizes are the most common and fit the majority of cribs available in the market. They adhere to federal safety standards and offer ease of compatibility with a wide range of cribs. When shopping for bedding or replacement mattresses, standard sizes are generally readily available, simplifying the process for parents.

Non-Standard Crib Mattress Sizes:

Non-standard crib mattress sizes include mini cribs, convertible cribs, and bassinets. Let’s take a look at how sizing differs:
  • Mini Cribs: Mini cribs are designed for smaller spaces and usually require a smaller mattress, often measuring around 24 inches in width and 38 inches in length. These cribs are a practical solution for parents with limited nursery space.
  • Convertible Cribs: Some convertible cribs may have unique sizing requirements for their mattresses. It’s essential to check the specifications provided by the crib manufacturer to ensure a proper fit during different stages of crib conversion.
  • Bassinets: Bassinets, designed for the earliest stages of infancy, also have their own unique mattress sizes. These dimensions can vary but are typically smaller than standard crib mattresses. Parents should check the specific measurements the bassinet manufacturer recommends for a secure and comfortable fit.
Understanding the difference between standard and non-standard crib mattress sizes is crucial when selecting a mattress for your baby’s crib. While standard sizes offer widespread compatibility and ease of bedding availability, non-standard sizes cater to specific crib designs or space constraints. Parents should carefully consider the dimensions recommended by the crib manufacturer to ensure a secure and comfortable fit for their little ones.


When choosing a mattress for your baby’s crib, it’s important to prioritize safety and comfort. A standard crib mattress is 27 1/4 inches by 51 5/8 inches, but be sure to measure your crib and choose a mattress that fits snugly. With these tips in mind, you can ensure your baby has a safe and comfortable sleep environment.