You order 'standard cot' sheets. They arrive. They don't fit — too long at one end, gaping at the corners, or so tight the elastic looks like it's about to give up entirely. This happens constantly, and it's not really your fault. 'Cot,' 'cot bed,' and 'bedside crib' get used almost interchangeably in everyday conversation, but the mattresses underneath them are genuinely different sizes.
Here's what each one actually measures, so the next set of sheets you order is the one that fits.
Bedside crib (Next to Me style)
This is the smallest of the three — the kind that attaches to the side of your bed for the newborn months, from brands like Chicco's Next2Me or Tutti Bambini's Cozee. Most sit at 51x85cm, though it's always worth double-checking the exact model, since a few variants run slightly different. It's a narrower, longer shape than a standard cot, which is exactly why generic 'cot size' sheets rarely fit it properly.
Standard cot
This is where things get genuinely inconsistent. A lot of full-size cots use a mattress around 120x60cm, but plenty of smaller cots and cribs sit closer to 90x50cm or 50x90cm depending on the brand and how the manufacturer labels it. 'Cot size' on its own isn't a fixed measurement — it's closer to a category than a spec, which is exactly the gap that generic sheets fall into.
Cot bed
A cot bed is the bigger, grows-with-your-child version — typically 140x70cm, and designed to convert into a toddler bed once the side comes off. It's longer and narrower than a standard cot mattress, not just a slightly bigger version of it, so cot sheets that fit your child at one year almost never fit the cot bed they move into afterwards.
Don't forget Moses baskets and travel cots
Two more shapes worth knowing, since they trip people up just as often: a Moses basket mattress usually sits around 30x76cm, much smaller and narrower again than a bedside crib, while a standard travel cot mattress is closer to 65x95cm. Neither is close enough to the others to share sheets, which matters if you're packing for a trip and assuming 'it's basically the same size.'
How to actually measure before you buy
Skip the box label and measure the mattress itself, in centimetres, length and width. If you're buying a fitted sheet or protector, also check the depth of the mattress against the pocket depth on the product listing — a shallow pocket on a thick mattress will pop off just as easily as the wrong length or width will. It takes two minutes with a tape measure and saves a return.
Why 'one size fits most' rarely does
A sheet that's even a little too big will bunch up or work loose overnight, which matters more for a baby who can't reposition themselves than it would for an adult. It's not really about tidiness — a properly fitted sheet is a genuine safety detail in a cot, not just a nicer-looking one.
This is also why we sell fitted sheets and mattress protectors as matched sets cut to the same exact measurements, rather than leaving you to cross-check two separate products against each other. It removes one more thing that can quietly go wrong between two items bought from different places.
Three stages, three different shapes, and none of them interchangeable — knowing which one you actually have is most of the battle. The rest is just a tape measure and a size chart, and a few extra minutes now that save you a return, or worse, a sheet that quietly comes loose at 3am.
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