Standard, Compact or Travel Cot? How to Identify Your Mattress Type Before Buying Sheets

Buying cot sheets would be simple if cot mattresses came in one size. They do not, and the word standard does a great deal of unearned work on product pages.

Two minutes with a tape measure will save you a return, and more importantly it will give you a sheet that actually fits, which matters more than comfort. Here is how to work out what you have.

Standard cot is not a size

This is the thing to understand before you shop. In Australia, all new and second hand cots must comply with a product safety standard, and that standard governs safety features rather than one fixed mattress footprint.

Household cots must comply with Australian Product Safety Standards, specifically AS/NZS 2172 in its 2003 edition, while portable cots are covered by AS/NZS 2195 in its 1999 edition. Those standards set out gaps between bars, depths and locking mechanisms. They do not mean every cot mattress in the country is identical.

So two cots both honestly described as standard can take noticeably different mattresses, and a sheet that fits one will be loose on the other. Loose is the problem, because a waterproof or fitted sheet that can ride up is a hazard rather than an inconvenience.

Why the fit is a safety matter

A sheet that pops off a corner can bunch near your baby's face. A sheet that is too large adds slack around the mattress edge, and that slack eats into the gap tolerance between mattress and cot side. Both are avoidable with the right size.

How to identify what you have

Work through these by feature rather than by what the box said, since the box is often long gone.

Treat those lengths as a way to tell the categories apart rather than as sizes to order from. Manufacturers differ, and the only number that matters is the one off your own mattress. Our Australian cot sheet sizes guide sets out the sizes we make and which mattresses they suit.

Measuring properly takes two minutes

Strip the mattress bare first, because measuring over an existing sheet will give you a reading that is slightly too big every time.

Measure the length along the longest edge, and the width across the narrowest point. Write both down in millimetres rather than rounding, since the difference between 690 and 710 is exactly the difference between a snug sheet and a loose one.

Then measure the depth, which is the dimension people forget. Stand a ruler against the side of the mattress and measure from the base to the top surface. Cot mattresses vary from quite thin to surprisingly deep, and a fitted sheet with a shallow skirt will not hold on a deep mattress no matter how good the elastic is.

Finally, check the gap. Red Nose advises there should be no more than a 20mm gap between the mattress and the cot sides, with a tip of no more than two finger widths. If your mattress already leaves a larger gap than that, the mattress is the problem rather than the sheet.

Our guide on choosing the right size waterproof fitted sheet walks through turning those three numbers into a size, and the waterproof sheet size guide covers the full range.

Travel cots, and the mattress question

Portable cots cause more confusion than every other category combined, and one particular question comes up constantly. The mat that comes with a travel cot feels thin and hard, so should you add a proper mattress?

No. This is the one place in cot bedding where the popular advice online is genuinely dangerous, and it is worth being direct about.

Red Nose advises using only the mattress supplied with the cot, and not adding extra mattresses or padding, as these can increase the risk of suffocation. The reason is specific to how these cots are built. A travel cot has soft, flexible sides, and a thicker mattress lifts your baby while creating a gap at the edge where they can become wedged between the mattress and the stretchy side.

The same applies to improvised padding. Folded quilts, foam toppers and cut up camping mats all do the same thing. Red Nose addresses the underlying instinct directly, advising that adding a custom foam layer is not advised as it may affect the mattress firmness, which is important for preventing suffocation risks, and that a mattress should not be elevated or modified in any way.

Firm feels uncomfortable to an adult hand. It is correct for a baby, and the thinness of a travel cot mat is a design decision rather than a cost saving.

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What to buy once you know your size

With three measurements in hand the rest is straightforward.

1. Buy for your measurement, not the category name. Ignore the word standard entirely.
2. Check the skirt depth. It needs to exceed your mattress depth with room to tuck.
3. Prefer fully encased elastic. Exposed elastic is a strangulation hazard in a cot.
4. Buy a travel specific sheet for a travel cot. A cot sheet will be loose on it.
5. Buy at least two of everything. One on, one in the wash.
6. Re check the fit after washing. Elastic relaxes over time.

If you are still in the bassinet stage, our bassinet sheet fit guide and guide to choosing bassinet sheets cover the smaller sizes, and when the time comes our notes on buying toddler bed sheets handle the step up.

Key points

1. Standard cot is a category, not a fixed mattress size.
2. Household cots must comply with AS/NZS 2172 in its 2003 edition.
3. Portable cots are covered by AS/NZS 2195 in its 1999 edition.
4. Those standards govern safety features rather than one mattress footprint.
5. A loose sheet can bunch near your baby's face.
6. An oversized sheet adds slack at the mattress edge.
7. Strip the mattress bare before measuring.
8. Record length, width and depth in millimetres.
9. Depth is the dimension most people forget.
10. Leave no more than a 20mm gap between mattress and cot sides.
11. Travel cot mattresses are thinner and usually a different footprint.
12. Use only the mattress supplied with a portable cot.
13. Never add an extra mattress, topper or foam to a travel cot.
14. A mattress should not be elevated or modified in any way.
15. Choose sheets with fully encased elastic.

Identifying your mattress type is really just three measurements and one decision not to improvise. Take the numbers off your own mattress, buy to those numbers, and keep travel cots exactly as the manufacturer supplied them. If you are unsure which of our sizes matches what you have measured, send us the dimensions and we will tell you honestly.