Cot mattress — Complete guide to Australian cot mattress sizes — standard (130×69cm), mini (120×60cm), and shaped — plus essential safety requirements on firmness, breathability, and fit to keep your baby safe during sleep.
Choosing the right cot mattress is one of the most important decisions new parents make. Your baby will spend between 14 and 18 hours per day on this mattress in the first months of life, making it crucial to get both the size and the safety specifications right. Unlike adult mattresses, cot mattress sizing in Australia is not regulated, which means dimensions vary between brands, and careful measurement is essential.
This guide covers all three Australian cot mattress sizes: standard, mini, and shaped, with exact dimensions, safety standards, and key factors to consider before purchasing.
The 3 Cot Mattress Sizes Available in Australia
1. Standard Cot Mattress — 130cm × 69cm
The standard Australian cot mattress is the most widely sold size. The standard dimensions are 130cm × 69cm (51.18″ × 27.16″), with a tolerance of ±1.5cm in either direction. Standard cot mattress thickness should not exceed 15cm (6 inches), with the most common thickness being around 10cm (4 inches). The gap between the mattress edge and the cot frame must not exceed 20mm on any side.
To test fit, press two fingers flat into the gap. If you can fit more than two fingers, the mattress is too small and presents a safety risk. Standard cot mattresses typically last from birth until your child is ready for a toddler bed, usually between ages 2 and 4.
2. Mini Cot Mattress — approximately 120cm × 60cm
Mini cots are compact alternatives ideal for smaller spaces or parents who want to keep their baby nearby. There is no regulated standard size for mini cot mattresses in Australia, but the most common dimensions are approximately 120cm × 60cm (47.24″ × 23.62″). The mattress supplied with mini cots is often too thin, so purchasing a separate replacement mattress provides better support and safety. Most babies outgrow mini cots by around 18 months.
3. Shaped Crib Mattresses
Shaped cot mattresses are available in circular, oval, and moon-shaped designs for specialty cots. There is no regulated size standard for shaped cribs. These mattresses are almost always sold together with the matching cot. Always use the manufacturer-supplied mattress unless a certified replacement is specified.
What to Look For When Buying a Cot Mattress
The following information is educational and does not replace advice from a qualified medical professional. Consult a paediatrician if you have concerns about your baby’s sleep safety.
Safety Standards
Australian and New Zealand regulations require cot mattresses to fit snugly into the cot frame — completely flat, with no soft inserts, and with no more than 20mm gap on any side. A larger gap creates a risk of the baby’s head or limbs becoming trapped. If your mattress no longer fits snugly due to age or shrinkage, it must be replaced. The mattress should also be certified to meet Australian Standards (AS/NZS 8811.1) where applicable.
Firmness
Firmness is a critical infant safety requirement. Soft mattresses increase the risk of Sudden Infant Death Syndrome (SIDS) by allowing infants to sink into the surface and re-breathe exhaled air. A cot mattress should spring back immediately when you remove hand pressure. If it takes several seconds to return to shape, it is too soft and should be replaced. This applies to foam, innerspring, and natural fibre mattresses alike.
Breathability
Breathable mattress materials reduce overheating risk and support SIDS prevention. The ideal sleeping temperature for babies is 20–22°C. Mattresses made from wool, organic cotton, or open-cell foam allow better airflow than dense synthetic foams. Look for mattresses with covers that are both breathable and waterproof. Quality cot mattresses achieve both.
Size Verification
Even when buying a “standard” cot mattress, always measure your cot’s interior base dimensions and compare them against the mattress specifications before purchasing. The ±1.5cm tolerance means two “standard” mattresses can differ by up to 3cm in length, which may be too loose in your particular cot. Measure the interior base of your cot and choose the closest matching mattress. When in doubt, opt for a slightly larger mattress rather than a smaller one, provided it can be inserted firmly without excessive force.
Conclusion
The right cot mattress combines correct sizing, adequate firmness, and breathable materials. The standard 130cm × 69cm size suits most Australian cots and will serve from birth through toddlerhood. For smaller spaces, a mini cot mattress around 120cm × 60cm is a practical alternative. Always verify fit with the two-finger test, ensure the mattress springs back immediately, and replace any mattress that fails either test. Your baby’s sleep environment is one area where there is no substitute for getting it right.
Related Articles
- Australia’s Best Cot Mattresses
- Australia Bed Size Dimensions: Mattress Guide
- Are Mattress Protectors Necessary?
For independent guidance on sleep and wellbeing, the Sleep Health Foundation is a good starting point.
