A waterproof fitted sheet has one job above all others: it keeps liquid off the mattress. That only works if the sheet fits the mattress snugly. Too big and it slips off the corners overnight, leaving the mattress exposed at the very moment you need it protected. Too small and it will not stretch over the depth, so it pops off the second someone rolls over.
Getting the size right is the difference between real protection and a sheet that bunches, gapes and lets accidents through. This guide runs through the standard Australian bed and cot sizes, shows you how to measure your own mattress, and points you to the right waterproof sheet size for each bed so you can buy with confidence.
Australian bed sizes at a glance
The measurements below are the approximate standard Australian sizes for each bed. They are a helpful starting point, but sizes vary between manufacturers, so always check your own mattress before you order. Pick the row that matches your bed, then follow the link to shop that size.
| Bed | Approx. mattress size | Shop |
|---|---|---|
| Bassinet | Varies by brand, check the mattress | Bassinet sheets |
| Compact/Travel Cot | Approx. 120 x 62 cm | Compact cot sheets |
| Standard Cot | Approx. 130 x 69 cm | Standard cot sheets |
| Co-sleeper | Varies by brand, check the mattress | Co-sleeper sheets |
| Single | Approx. 188 x 92 cm | Single sheets |
| King Single | Approx. 203 x 107 cm | King single sheets |
| Double | Approx. 188 x 137 cm | Double sheets |
| Queen | Approx. 203 x 153 cm | Queen sheets |
| King | Approx. 203 x 183 cm | Shop all sizes |
If your bed sits between two of these sizes, or you have an older mattress that does not match the current standards, measuring is the only way to be sure. Here is how to do it in a minute.
How to measure your mattress
You need three numbers: length, width and depth. A tape measure and a flat mattress are all it takes.
- Length: measure the longest side, from the top edge to the bottom edge.
- Width: measure the shortest side, from one long edge across to the other.
- Depth: measure the height of the mattress from the base up to the top surface, holding the tape straight against the side.
Length and width tell you which size to choose. Depth is the number most people forget, and it matters more than you might expect. A fitted sheet has to wrap under the mattress to stay put, so the deeper the mattress, the more sheet it uses.
This is why depth matters so much for pillow-top mattresses. A pillow-top adds a thick, padded layer on top, which can push the total depth well past a standard mattress. A sheet cut for a slim mattress will strain over that extra height and ping off the corners. If you have a pillow-top or a particularly deep mattress, note the depth and check it against the size you are considering so the sheet has enough stretch to hold on.
Baby sizes: bassinet, cot and co-sleeper
Baby bedding is where sizing catches most parents out, because the small sizes are the least standardised. A standard cot in Australia is close to 130 x 69 cm, and a compact or travel cot is close to 120 x 62 cm, so those two are fairly predictable.
Bassinets and co-sleepers are a different story. Both come in a wide range of shapes and sizes that vary by brand, and some are oval rather than rectangular. There is no single standard to rely on, so measure the mattress that came with your bassinet or co-sleeper and match it to that, rather than assuming one size fits all. A snug fit here is not just about protection: a loose sheet on an infant sleep surface is a safety concern, so this is one size worth getting exactly right.
Kids and adult sizes: single through king
Once children move out of a cot, most go into a single (approx. 188 x 92 cm) or a king single (approx. 203 x 107 cm), which gives a growing child extra length. These two sizes cover the majority of kids' beds and are the most common choices for toilet training and the bedwetting years.
Adult beds run from double (approx. 188 x 137 cm) up through queen (approx. 203 x 153 cm) to king (approx. 203 x 183 cm). A waterproof sheet is not only for children: it protects an adult mattress from spills, night sweats and incontinence just as well, and doubles as a waterproof mattress protector in a single layer. You can browse every size in the waterproof bed sheets collection.
Still not sure?
If your bed is an odd shape, sits between sizes, or you simply want a second opinion before you buy, use our size finder tool. Answer a couple of quick questions about your bed and it will point you to the right size, so you are not guessing from a tape measure alone.
The size finder is the fastest route when a mattress does not match the standard numbers, and it is there for the tricky bassinet and co-sleeper sizes too.
A waterproof sheet only earns its place when it fits. Measure once, match it to the right size, and you get a snug fit that stays on the mattress all night and keeps the surface underneath dry. When you know your size, head to the find your sheet size page or shop your bed directly from the table above.
