How to find the right size sheet for your cot, bassinet or co-sleeper.
Key takeaways
-
A fitted sheet should be firm and flat, with no loose fabric.
If it bunches, slips or needs tucking to stay put, it's the wrong size for that mattress. -
Size the sheet to the mattress, not the cot.
Every cot sold in Australia states its recommended mattress size. For bassinets and co-sleepers, measure the mattress itself, not the outside of the frame. -
Standard Australian cot mattresses are 130 x 70 cm (with a 1 - 2 cm variance on either dimension considered acceptable).
Bassinets, co-sleepers and mini cots have no agreed size, which is where most sizing mistakes happen. -
The question worth asking:
Does this product help reduce the risk of rebreathing, and has it been tested?
Picking the right sheet for your baby's cot shouldn't take an afternoon. But one Google search and you're down a rabbit hole of measurements, safe sleep tips and mum forums. If that's where you are, it isn't you: sizing genuinely is confusing. Here's what actually matters, what to check, and the quickest way to find a sheet that fits.
A properly fitted sheet is essential for safe sleep
Safe sleep guidance from Raising Children Network recommends keeping the sleep space clear of doonas, pillows, cot bumpers, mattress padding, lambswool underlays and soft toys. Your baby's head and face should stay uncovered.
The same guidance describes the safest surface as a firm mattress with a tight-fitting fitted sheet. A sheet that's too big or too small can bunch on the surface or ride up at the sides as your baby moves, which increases the risk of fabric covering their face. If you find yourself tucking excess fabric under to make a sheet behave, treat that as a sign it's the wrong size.
The right sheet should sit as flat and taut as the mattress underneath it.
Why it's difficult to know which size sheet to buy
Sizing is the question we get asked more than any other at Little Human Linens. So if you're stuck, you're in good company.
Cots are the easier part. Most Australian and US cot manufacturers make their mattresses to an agreed standard size, give or take 1 to 2 cm, though a few brands make larger cots. Since 19 January 2026, every cot sold in Australia must meet the mandatory infant sleep products safety standard, which requires a firm sleep surface and compliance with recognised firmness standard AS/NZS 2172:2013 [1,2] or the newer AS 5407.1 which has superseded AS/NZS 8811.1:2013 [3].
Bassinets, moses baskets, pram mattresses and co-sleepers are a different story. There's still no agreed size, so dimensions vary from brand to brand. Shapes vary too: some mattresses are rectangular, some oval. With so many brands and models on the market, it's no surprise that working out which sheet to buy feels harder than it should.
Start with the mattress, not the frame
A sheet only has to fit one thing: the mattress. So that's where to start.
For a cot, check the safety label. Cots sold in Australia carry a label stating the recommended mattress size, and that measurement tells you which sheet you need.
That mattress also needs to fit the cot properly, with no more than a 20 mm gap between the mattress and the cot sides and ends. Raising Children Network's guide to safe cots and mattresses covers what to check. If the mattress doesn't fit the cot, no sheet will fix that.
For bassinets and co-sleepers, be wary of the dimensions on the box. Manufacturers often quote the external size of the whole bassinet rather than the mattress inside it. Measure the mattress length, width and depth. Depth matters more than people expect: a thicker mattress needs a sheet with sides deep enough to wrap underneath.
Our five sheet sizes and what they fit
If you already know your mattress size, this is the quick version. Every measurement below is the sheet, not the mattress.
| Sheet | Our Size | Made to fit |
|---|---|---|
| Small Bassinet | 81 x 41 x 10cm | Traditional bassinets, moses baskets, pram bassinets and the Snoo, with mattresses up to 5 cm thick |
| Co-Sleeper | 85 x 51 x 17cm | Co-sleepers and bedside bassinets, larger European bassinets and change pads |
| Mini Cot | 120 x 62 x 20cm | Mini and compact cots and some travel cots, about 10 cm shorter and narrower than a standard cot |
| Standard Cot | 132 x 71 x 20cm | Standard Australian and US cots with a 130 x 70 cm mattress |
| European Cot | 142 x 71 x 20cm | European cotbeds and larger cots with a 140 x 70 cm mattress |
Our sheets are cut rectangular, but they'll also fit an oval mattress where the length and width are close to the sheet's. For a brand-by-brand list of what fits each size, see our size information page.
The sheet is part of the sleep surface
There's one more reason the sheet itself matters, and it's a newer one. In May 2026, Standards Australia published AS 5407.3, the world's first national standard for testing CO₂ rebreathing risk in infant sleep products [4]. It tests products in combination (mattress, sheet and any protector together) because that's how babies actually sleep on them.
That's a useful way to think about the sheet. It isn't a finishing touch on top of the mattress; it's part of the surface your baby sleeps against. We cover what the standard measures, and what it means for bedding you already own, in our AS 5407.3 explainer.
None of this replaces the basics: baby on their back, on a firm flat surface, in a clear cot, with their face uncovered. Those are still the most protective things any parent can do.
Find your sheet size in under 30 seconds
Whether you're a parent-to-be, a new parent or onto your third baby, you've got enough on your plate. So we've made finding the right size quicker than folding a pile of laundry.
We've gathered manufacturers' measurements for the cots, bassinets and co-sleepers families ask us about into our sizing tool. Choose your brand and model, and it tells you which sheet fits. If your model isn't listed, or you've got an older or second-hand cot, send us your mattress measurements and we'll help you work it out.
Find your fit in less than 30 seconds.
About the author
Kellee Eriksson is the founder of Little Human Linens, an Emergency Nurse with 15+ years of clinical experience, and an INPAA (Infant and Nursery Products Alliance of Australia) Baby Safety Ambassador. She participated in industry consultations during the development of Australia's 2026 infant sleep surface safety standards and is actively involved in the current rollout. She built Little Human Linens because safe sleep products should be easy to find, easy to understand, and easy to trust.
References
- Consumer Goods (Infant Sleep Products) Safety Standard 2024. Federal Register of Legislation, F2025C00270. Australian Government.
- Standards Australia / Standards New Zealand. AS/NZS 2172:2013 — Cots for household use: Safety requirements.
- Standards Australia. AS 5407.1 — Methods of testing infant sleep surfaces (firmness).
- Standards Australia. AS 5407.3 — Methods of testing infant sleep surfaces, Method 3: Test for carbon dioxide and associated requirements.
