Cot Mattress Size Guide & Dimensions (Australia)


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Do you have a new baby on the way? If so, congratulations! One of the essential items you will need to purchase for your little bundle of joy is a cot mattress – it is where your infant will be spending approximately 14 to 18 hours a day when you first bring him or her home.

You may have already picked the cot bed and are searching for the right cot mattress to go with it, or you may be starting from scratch. Either way, in this guide, we discuss different cot mattress sizes available in Australia and factors to consider when making your purchase.

Note: Crib and cot mean the same thing and are often used interchangeably. While crib is commonly used in the US and Canada, the cot is more prevalent in Australia and the UK.

cot mattress size Australia-header

Cot Mattress Sizes Chart Australia (AU)

Size NameDimensions (cm)Dimensions (Inch)
Standard130 x 69 cm ±1.5cm51.18″ x 27.16″ ±⅝ inch
Mini120 x 60 cm47.24″ x 23.62″

Different Cot Mattresses Sizes in Australia

Not all cot mattresses are of the same size. In fact, there are three different sizes of cot mattresses that are popular in Australia – Standard, Mini and Shaped. Also, as the size of cot mattresses isn’t regulated (unlike regular mattresses) in Australia, some brands may slightly differ in size from others.

A cot mattress that is too small or large can pose a safety hazard for your child, so it is crucial to pick the right size.

1. Standard Cot Mattress Size

Baby Cot bed & mattress dimensions

The standard cot mattress is the most popular size in Australia as it’s big enough to last your child until he or she is ready for a bed.

The size of a standard cot mattress in Australia is 130 x 69 cm or 51.18” x 27.16” with a tolerance of “plus-minus” 1.5cm or ⅝ inch along length or width. An Australian standard cot fits a standard cot mattress. The thickness of the standard cot mattress should not exceed 15 cm or 6”, and the most common thickness is 4” (thicker isn’t always better).

There can be a little variance in sizes between brands, but the distance between the mattress and cot frame should never be over 2 cm. A good way to check the fit is by placing two fingers between the mattress and cot bed. If you can fit more than two fingers, the mattress is small and can be a suffocation or entrapment hazard for the baby.

2. Mini Cot Mattress Size

As you’d have already guessed, a mini cot mattress is a smaller version of the standard cot mattress and is perfect for kids who have outgrown their bassinet or Moses basket. Most mini cots come by default with a mattress, but often it’s too thin or not too comfortable.

The size of mini cot mattresses isn’t regulated in Australia (or worldwide), but they typically measure 120 x 60 cm or 47.24″ x 23.62″.

Mini cots are smaller and cheaper than the standard size and ideal for tight spaces. It’s also an excellent option if your newborn will be sharing space with a sibling or yourself. They have the additional benefit of being portable and can be easily moved from room to room for convenience. Babies typically outgrow mini cot mattresses in 18 months, while they can use a standard cot mattress until they are three to four years old

3. Shaped Crib Mattress Size

While standard and mini cot mattresses are rectangular, shaped cot mattresses can be circular, oval, moon-shaped etc. They are a great option if you’re looking for something fancy or unique. As there is no regulation or specification pertaining to the dimensions of the shaped cots, such mattresses are mostly sold along with the cot. 

Other Factors to Consider when Buying a Cot Mattress

Note: While we want to assist in providing educational information, this is not meant to replace medical advice from a trained professional. Please speak to a medical professional regarding any questions regarding your child’s sleeping habits.

Now that you know about the different types and sizes of cot mattresses available in Australia, here are some other factors you should consider before making your purchase:

1) Safety Standards

We understand your priority is ensuring the safety of your young one as he or she sleeps. Australia and New Zealand have a set of regulations to confirm the safety of your child’s cot. A safe cot is outfitted with a single, firm mattress that fits snugly within the cot and lays flat. If there is more than 20 mm of space between the edge of the mattress (all sides) and the cot frame, it is not a safe mattress and needs to be replaced with a larger size. If the mattress is not flat and has any dips or elevation points, it’s also an indicator it needs replacement. The purpose of the safety standards is to minimise the possibility of falls, entrapment, and caught clothing which can be fatal to infants.

TIP: If you can’t buy a new cot, second-hand cots are not a problem as long as they meet the current safety standards. However, it is not recommended to use used mattresses for your child as they may not be as firm and could also have bacteria, fungi, or mould that can be dangerous to the health of your child.

2) Firmness

Getting a softer mattress for comfort may seem preferable, but this can be a danger to newborns. Sudden Infant Death Syndrome (SIDS) is the unexpected death in children under one year of age and often results from poor respiration, typically while they sleep, which is why it’s also called “crib death.” One way to minimise the risk of SIDS is by ensuring your cot has a firm mattress. A mattress that’s too soft risks the possibility of rebreathing for infants while stomach sleeping, which entails the child inhaling the same exhaled air, so they aren’t getting enough oxygen.

To see if the mattress you’ve selected is firm, apply pressure to the mattress with your hand and see how the mattress reacts when you remove it. If the mattress immediately springs back into place, it is firm; if the mattress takes a little more time to return to its original position, your mattress is likely too soft and should be replaced with a firmer model.

3) Breathability

Mattresses that are made with a breathable material also have safety standards in mind. Those made with breathable materials may reduce the risk of SIDS while also preventing your baby from getting too warm at night. The optimal temperature for a sleeping baby is between 20 – 22℃. The best breathable materials are organic cotton or wool.

4) Size

As discussed above, adequate sizing also plays a role in safety. An ill-fitting mattress with too much gap between the mattress’s edge and the cot frame increases the chances of entrapment. Even a mattress that fits well, but is constructed of soft foam or has flexible inner springs, may not be of adequate size when it’s time to lay your child down to sleep.

A safe mattress will not have more than 20 mm of space between the edge of the mattress and the cot. This means if you have more than two fingers width of space between the mattress and the cot, the mattress is ill-fitting and should be replaced with a proper size.

Wrapping Up

Now that you are informed, you can utilise this newfound knowledge and confidently purchase the right cot mattress that’s comfortable and safe for your child. You can also check our picks for the top cot mattress options in Australia here.

We hope this article was helpful in better understanding cot mattress dimensions in Australia and everything you need to know before making a purchase! If you have any questions or would like to share your experience, please leave us a comment below!

James Lee

James Lee

James is the content director at WhatASleep, a certified sleep science coach from Spencer Institute and our in-house sleep product expert. Over three years, he's personally tested hundreds of mattresses. He likes to keep his reviews simple, objective, and straightforward so that the readers don't have to go through decision fatigue which is often the case while shopping for sleep products.

He hails from Sydney and has a journalism degree from the University of Queensland and an MBA from Melbourne Business School.


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