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Choosing the Right Standard Crib Mattress Size: A Comprehensive Guide for Parents



When preparing your nursery for a newborn baby, one of the key items you’ll need to purchase is a crib mattress. Crib mattress size is an important factor to consider to ensure a proper fit and your baby’s safety. This article provides a comprehensive overview of standard and non-standard crib mattress dimensions, types of mattresses, safety regulations, and tips for choosing the right size.

Standard Crib Mattress Dimensions

Crib mattresses are manufactured in standard sizes to fit most cribs sold in the US and Canada. Understanding the common length, width, and thickness dimensions will ensure the mattress you select fits snugly into your crib frame.

Common standard dimensions for crib mattresses are:

  • Length – 51 5/8 inches (131 cm)
  • Width – 27 1/4 inches (69 cm)
  • Thickness – Ranges from 4 to 6 inches

Fit is essential not only so your crib mattress doesn’t slip and move around, but also to prevent dangerous gaps that could trap your baby’s limbs or allow them to get stuck between the mattress and crib sides.

Standard crib mattresses are available in two styles:

  • Fitted crib mattresses have elastic corners that hold the mattress securely in place on all sides. This helps prevent gaps and slippage.
  • Non-fitted mattresses are flat pads without elastic corners. These require checking for a flush fit all the way around the crib interior before use.

Crib and Mattress Safety Standards

Various oversight organizations regulate standards for cribs and mattresses to ensure infant safety. Understanding what these mandatory and voluntary safety standards cover can give you peace of mind you’re choosing quality products for your baby.

In the United States, the Consumer Product Safety Commission (CPSC) issues federal mandatory safety standards under the Consumer Product Safety Improvement Act regarding cribs and related infant products like mattresses and bedding.

For crib mattresses, key CPSC regulations require:

  • Fire safety – Mattresses pass flammability standards without the use of potentially harmful flame-retardant chemicals.
  • Firmness – Appropriately firm surface for baby depending on product claims. Cannot be excessively soft or contain deep crevices.
  • Fit – Must completely fit crib interior with no hazardous gaps.
  • Lead and phthalates – Strict limits on lead, phthalates, and other toxic heavy metals and chemicals.

The Juvenile Products Manufacturers Association (JPMA) also oversees a certification program in the US and Canada with robust crib and mattress standards beyond government requirements. JPMA tests for durability, structural integrity, and other safety hazards. Their certification mark indicates adherence to the latest voluntary standards.

Types of Crib Mattress by Material

You’ll also want to evaluate different crib mattress materials and types when selecting the right one your for your baby registry. Models made with different internal construction and surface materials have pros and cons regarding cost, durability, breathability, hygiene, and more.

Innerspring/Coil Mattresses

The most common type of crib mattress uses steel coils or springs in the interior construction with cushioning layers up top.


  • Firmer support
  • More breathability from space between coils
  • Lower cost price point


  • Coils can sag over time
  • Less contouring to the baby’s body
  • Springs may poke through surface fabric

Foam (Memory Foam vs Standard)

All-foam mattresses provide a flat, even surface without internal springs. Memory foam and standard foam options are available:

  • Memory foam molds closely to the baby’s shape for customized alignment and pressure relief.
  • Standard/basic foam tends to be firmer but less contouring. Often budget-friendly.

Foam mattress pros:

  • Lightweight design is crucial for a baby’s crib mattress
  • Easy to clean waterproof cover
  • Hypoallergenic options reduce irritants and allergens
  • Some plant-based, eco-friendly foams are available

Potential cons:

  • Traps more heat than breathable coils
  • Some less expensive foam compacts easily

Organic Materials

Eco-conscious parents may prefer crib mattresses made with sustainable organic materials:

  • Organic cotton coverlets and fill prevent pesticide residue from contacting the baby’s skin.
  • Natural wool brings moisture-wicking, thermal regulation, and antimicrobial properties to a baby’s crib mattress.
  • Coconut coir offers a resilient springy core, like latex but vegan.

Benefits of organic crib mattresses:

  • Sustainably-sourced materials
  • Hypoallergenic for sensitive skin
  • Renewable and biodegradable
  • Free of polyurethane foams made from crude oil


  • Priced higher than foam and coil options
  • Materials like latex or wool can still trigger allergies

Natural Latex

Sourced from rubber tree sap, 100% natural latex has an exceptional combination of cushiony contouring and support. Available in both all-latex mattresses or latex-coated coil springs.

Latex mattress advantages

  • Responsive spring-back and body-molding
  • Sleeps cool and breathable
  • Long-lasting over 8+ years
  • Safe hypoallergenic material

Considerations when you choose a crib mattress

  • On the higher end of crib mattress prices
  • Verify certification for purity—synthetic latex blends also exist, important for choosing a baby crib mattress to ensure it meets the crib mattress size is 27 by 52 inches standard.

Adjustable Size Mattresses From Infant to Toddler Stages

Investing in a size adjustable crib mattress enables safely extending the longevity of your crib use. Adjustable mattress bases expand in width AND length as your little one grows from newborn to toddler.

Rather than purchasing a separate infant then toddler mattress or having to transition them to a big-kid bed sooner than you’d like, adjustable mattresses save money and allow kids to remain sleeping comfortably in their crib for longer.

Some of the top brands offering adjustable crib mattresses include:

  • Natart Juvenile: Twice the value with their Serenity adjustable crib mattress starting from newborn size at 38 x 24 inches up to 50 x 30 inch toddler dimensions. Made with 5 inches of high-density foam and waterproof cover. Priced around $250.
  • Dream on Me: Their 3” Playard Mattress ranges from 32.5 x 19 inches up to 38 x 25 inches with included elastic for foldable pack ‘n play/travel cribs. Very affordable under $100.
  • Moonlight Slumber: On the luxury end, their All Foam Adjustable Crib Mattress starts at 37 x 24-inch newborn dimensions and expands to 50 x 30 toddler size. Made with medical-grade foam and antimicrobial waterproof surface. Cost over $300.

While adjustable crib mattresses carry a higher price tag than fixed size, they offer great bang for buck by extending your investment across the first several years of your child’s life.

Non-Standard Crib Mattress Dimensions

While standard cribs and mattresses are by far the most common, you may also come across several specialty or non-standard mattress sizes:

  • Mini crib mattresses – For smaller “mini” or portable crib options. Often 38 inches long x 24 inches wide.
  • Oversized crib mattresses – Extra thick mattresses at 8+ inches might require deeper 54-inch long crib frames with 28 – 32 inch widths, suiting a baby crib mattress.
  • Round or oval crib mattresses – Shaped to fit specific decorative or heirloom crib styles.
  • Custom mattress sizes – Special medical needs or in-home daycares may require custom crib mattress dimensions.

The first step is always ensuring you have the exact interior dimensions of the crib itself, so any non-standard sizes can be custom ordered or altered from a larger stock mattress to perfectly size down to safe dimensions. Medical supply companies, specialty juvenile brands and even local mattress alteration shops can all help with sourcing unusually sized crib mattresses.

Tips for Finding the Right Crib Mattress Size

Here are some top tips when evaluating crib mattress sizes for your nursery:

  • For standard cribs, reference the common 51 5/8” x 27 1/4″ dimensions when buying online or in-store.
  • Take exact interior measurements of your crib width between slats and length from end-to-end if unsure.
  • Look for the Cert
  • Look for the Certification mark from JPMA-compliant brands ensuring quality standards are met.
  • Evaluate whether you want the convenience of a mattress with elastic corner fittings to hold it snugly in place within your crib rails.
  • Assess different crib mattress materials like coils, foam, latex, and organic components based on price points, benefits, and tradeoffs.
  • Prioritize non-toxic materials like food-grade polyethylene covers instead of cheaper plastics containing phthalates and lead.
  • Consider splurging on an adjustable-size mattress to accommodate growth from newborn to toddler years, maximizing your investment.
  • For non-standard mattress sizes, confirm exact dimensions of the specialty crib’s interior width and length.
  • Waterproof crib mattress protectors add an extra moisture barrier for accidents and spit-ups without changing feel.
  • Make sure any mattress fully fits side-to-side, end-to-end, with no gaps wider than two fingers that could trap limbs.
  • Buy from reputable brands and retailers that stand behind their quality and safety guarantees, particularly for mattress and crib purchases.

Common Questions About Crib Mattress Sizes

Here are answers to some frequently asked questions around sizing, dimensions and safety when shopping for the essential baby registry buy of a crib mattress:

What are the typical dimensions of a standard crib mattress?

  • The commonly accepted standard size is 51 5/8 inches long by 27 1/4 inches wide. Thickness ranges from 4 to 6 inches.

Are bigger or thicker crib mattresses safer for the side of the crib?

  • No research conclusively supports that bigger is safer. An overly thick mattress leaves dangerous gaps. Prioritize quality materials and exact fit.

When should I size up to a toddler mattress vs a crib mattress?

  • When your child reaches 35 inches tall or starts attempting to climb out of their crib, it’s time to transition to a toddler bed.

How do I know if an organic or eco-friendly crib mattress is truly “green”?

  • Credible ecolabel certifications like GOTS (Global Organic Textile Standard) or CertiPUR-US certified foam offer third party validation of environmental claims and are essential considerations when you choose a mattress.

Can I just cut a non-standard mattress down to size to fit an oddly shaped crib?

  • Never attempt this yourself as it poses suffocation and entrapment hazards. Consult a mattress alteration specialist to professionally resize abnormal dimensions.

What’s the best type of crib mattress?

There is no definitive “best” pick with one standout feature coming at the cost of others. Here is how leading options stack up:

Mattress TypeProsCons
Coil/InnerspringTraditional firm support Many budget optionsCan feel hard Less contouring
FoamModern material Light, easy to clean Custom firmnessHeat retention Off-gassing concerns Cheaper = less durable
OrganicEco-friendly materials Natural temperature regulationExpensive Limited availability
AdjustableGrows in size with child Extended valueHigher investment Upfront Sizing limitations

Look for safety certifications first when deciding what’s “best” based on your priorities around price, materials, quality, convenience and environmental factors.

Safe Sleeping Tips

Safe Sleeping Tips: When it comes to ensuring a safe sleep environment for your baby, the crib and the mattress play a crucial role. It is important to choose a crib mattress that fits snugly in the crib to prevent any gaps where a baby could get trapped.

  • The standard-sized crib mattress size is 28 inches by 52 inches, while a mini crib mattress size is 24 inches by 38 inches. When purchasing a mattress, it is essential to consider the dimensions of a standard size crib to ensure a proper fit.

A crib mattress should be firm to provide a safe sleeping surface for your baby. Avoid using a soft mattress that could increase the risk of Sudden Infant Death Syndrome (SIDS).

Different crib sizes mean that crib mattresses can vary in size, so be sure to measure the crib you choose before purchasing a mattress. A properly sized mattress can help prevent accidents and ensure your baby sleeps comfortably and safely.

FAQ – Crib Mattress Size

1. What is the standard size of a crib mattress?

The standard crib mattress size is 28 inches in width and 52 inches in length. It is important to ensure that the mattress fit snugly within the crib to prevent any gaps that could pose a safety risk to the baby.

2. How do I choose the right crib mattress size?

When selecting a crib mattress, measure the interior dimensions of the crib to ensure you get the correct crib mattress size. It should fit tightly without leaving any gaps between the mattress and the crib.

3. Are there different types of crib mattresses available?

Yes, there are various types of crib mattresses such as organic mattresses, breathable crib mattresses, and firm mattresses designed to cater to different needs and preferences.

4. What is the size of a mini crib mattress?

A mini crib mattress typically measures around 24 inches in width and 38 inches in length, making it smaller than a standard crib mattress.

5. How can I ensure I choose the best crib mattress for my baby’s crib?

Consider factors such as mattress cover, breathability, and the firmness of the mattress to select the best crib mattress that meets the safety and comfort requirements for your baby’s crib.

6. What should be the right thickness of a standard crib mattress?

A standard-size crib mattress typically has a thickness of around 6 inches, providing adequate support for the baby while sleeping.

Bottom Line on Crib Mattress Size

Selecting the perfectly sized crib mattress ensures your baby’s sleeping space stays snug and secure. By understanding standard mattress dimensions of 51 5/8’’ x 27 1/4’’ and varying materials from traditional coils to fabrics like latex and foam, you can find the right crib mattress to nurture restful nights.

Specialty sizes for portable or extra-large cribs may vary, so always measure interior dimensions first. And look for safety features like waterproofing, high-density constructions for firmness, and certifications from organizations like the Juvenile Products Manufacturers Association.

Proper sizing and quality touches offer peace of mind your crib mattress supports safe slumber during your baby’s exciting growth from newborn nursery days through the toddler transition.

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