Toddler Bed Sizes Explained: What Size Bed Does Your Child Need?

TL;DR: A standard UK toddler bed takes a 140 x 70cm mattress, the same size used by most cot beds, which is exactly why a child can often move from a cot bed straight into a toddler bed without needing a new mattress. This is smaller and a different shape entirely to a standard single bed, which takes a 90 x 190cm mattress instead. The mattress size is only part of the picture though, since the bed frame itself, including any guard rails, will always be a little larger than the mattress alone, so it's worth checking the full frame dimensions before you buy, not just the mattress size.

Toddler bed sizing causes more confusion than it should, mostly because it sits right between two other sizes, a cot and a single bed, without matching either one exactly. Here's a proper breakdown of toddler bed sizes and what they actually mean for your child's room.

What Size Is a Toddler Bed?

A UK toddler bed is built around a 140 x 70cm mattress. This is the standard cot bed mattress size, and it's the size used across most toddler beds on the market, including the entire toddler bed range at Prime Baby Gear. The frame itself, once you include the guard rails and headboard, is naturally a bit larger than the mattress dimensions alone, so always check the full assembled size listed on the product page rather than assuming the mattress size and the overall footprint are the same thing.

Toddler Bed Size vs Cot and Cot Bed Size

This is where the size question usually starts. A standard cot typically takes a 120 x 60cm mattress, a slightly smaller size than a cot bed. A cot bed steps up to the larger 140 x 70cm mattress, and a toddler bed matches that same 140 x 70cm size exactly. This isn't a coincidence: it's specifically why a child moving from a cot bed into toddler bed mode, or into a separate standalone toddler bed, can often keep using the same mattress rather than buying a new one at that stage.

Toddler Bed Size vs Single Bed Size

A standard UK single bed takes a 90 x 190cm mattress, which is a completely different shape to a toddler bed's 140 x 70cm, not just a bigger version of it. A single bed is longer and narrower, built for a child who's grown considerably taller, while a toddler bed is shorter and wider, built around a younger child's smaller frame. This is why moving from a toddler bed to a single bed always means buying a new mattress, unlike the cot bed to toddler bed move, where the size often carries over.

Real Toddler Bed Sizes at Prime Baby Gear

Every toddler bed in the current range uses the same 140 x 70cm mattress size, so the choice between them comes down to style rather than size. The OBaby Maya Toddler Bed keeps a simple, low-profile Scandinavian frame at £180. The OBaby Gatsby Toddler Bed, also available in pink, and the OBaby Lumi Toddler Bed in grey or pink both sit at £290, with a more upholstered, velvet finish. Whichever you choose, the mattress fits the same way, so it's worth measuring the room around the full frame size listed on each product page rather than the mattress alone.

Why the Mattress Size Alone Doesn't Tell You Everything

Two toddler beds using the identical 140 x 70cm mattress can still take up noticeably different amounts of floor space once you account for the frame, headboard, and guard rails around it. A simpler frame with a low headboard will generally sit closer to the mattress dimensions, while a more decorative or upholstered frame can add a meaningful amount of extra length and width. Always check the assembled size listed on the specific product page before buying, particularly if the room you're furnishing is on the smaller side.

When Does a Toddler Bed Become Too Small?

Most children outgrow a toddler bed's 140 x 70cm size somewhere between age 4 and 6, though this varies depending on how tall your child is rather than age alone. There's no strict cut-off, but once your child's feet are regularly reaching the end of the mattress or they've simply outgrown the frame's guard rails and low height, it's a reasonable sign that a full single bed is the next step.

How to Measure Your Room Before Buying

Measure the length and width of the space you're planning to use, including enough clearance for a door or wardrobe to open fully, then compare that against the full assembled dimensions listed on the product page rather than the mattress size alone. It's a small extra step, but it avoids the common mistake of a toddler bed technically fitting the floor space while leaving no room to actually walk around it comfortably.

Final Thoughts

Toddler bed sizing is simpler than it first appears once you know the numbers: 140 x 70cm for the mattress, matching most cot beds, and noticeably different to a single bed's 90 x 190cm. The frame size is what actually determines how much room a toddler bed needs day to day, so always check the full assembled dimensions rather than assuming the mattress size tells the whole story.

Frequently Asked Questions

What size is a toddler bed? 

A standard UK toddler bed takes a 140 x 70cm mattress, the same size used by most cot beds, though the full bed frame is a little larger once guard rails and a headboard are included.

Is a toddler bed mattress the same size as a cot bed mattress? 

Yes, in most cases. Both typically use a 140 x 70cm mattress, which is why a mattress can often move from a cot bed into a toddler bed without needing to be replaced.

Is a toddler bed the same size as a single bed? 

No. A single bed takes a 90 x 190cm mattress, a longer and narrower shape built for an older child, compared to a toddler bed's shorter, wider 140 x 70cm size.

How do I know if my child has outgrown their toddler bed? 

Most children outgrow the 140 x 70cm size somewhere between age 4 and 6, often signalled by their feet reaching the end of the mattress or simply feeling cramped by the frame's guard rails.

Does every toddler bed use the same size mattress? 

Most UK toddler beds do use the standard 140 x 70cm size, but always check the specific product page to confirm, since the overall frame dimensions can still vary between styles.