So here’s the thing no one really tells you when you’re setting up the crib at 10 p.m. with a half-assembled Allen wrench in one hand and a baby monitor in the other: mattress sizing is weirdly important. Not just for safety, but also for your own sanity. A cot mattress that’s too small leaves awkward gaps. Too big, and you’re stuck playing mattress Tetris every time you change a sheet.
If you’re deep in this rabbit hole already, maybe start with this quick guide on how to choose the best crib mattress — it lays out some helpful basics.
And if you’re just looking for safe crib mattress options because honestly, you just want to check this off the list, here’s a shortcut: safe crib mattress options.
H2: Understanding Cot Mattress Dimensions
Standard Cot Mattress Sizes
Here’s where things get a little less straightforward than you’d think. Cot mattresses don’t come in one universal size. But there are common standards — depending on where you are and what kind of cot or crib you’re using. Some of the most typical sizes include:
- 60 x 120 cm (23.6 x 47.2 inches) — This is the standard cot size in the UK and pretty common in Europe.
- 52 3/8 x 28 inches — This is the U.S. standard crib mattress size, as outlined in the CPSC crib mattress regulations. Max thickness should be 6 inches.
- 50 x 27.5 inches — Sometimes used for mini cribs or compact designs, but not as widely adopted.
These sizes are designed to fit snugly within the cot frame, which helps reduce suffocation and entrapment risks. If you’re wondering how this compares to a full crib setup, this might help: what are the dimensions of a crib mattress.
Cot Bed vs. Cot Mattress Measurements
This is one of those things that sneaks up on you. You buy a cot bed thinking you’re planning ahead (because it turns into a toddler bed, right?), but then the mattress doesn’t fit the same way. The names sound similar, but the sizes? Not always.
Type | Typical Dimensions | Notes |
Cot Mattress | 60 x 120 cm (23.6 x 47.2 in) | Standard infant size |
Cot Bed Mattress | 70 x 140 cm (27.6 x 55.1 in) | Designed to last through toddler years |
According to the Federal Register crib mattress standard, mattresses must fit snugly in both standard cots and larger cot beds to meet safety guidelines. If you’re thinking long-term, those top-rated convertible cribs (link here) might be worth a look. Just double-check the mattress size needed before you buy.
And if you’re thinking ahead to toddler beds, this might help too: will a crib mattress fit a toddler bed?
Region-Specific Cot Mattress Sizes
This part matters more than people think, especially if you’re ordering from another country or inheriting a hand-me-down. Cot mattress sizes shift a bit depending on where you’re living. Here’s a quick look:
Region | Typical Cot Mattress Size |
US | 52 3/8 x 28 inches |
UK | 60 x 120 cm (23.6 x 47.2 in) |
Australia | 68.5 x 137 cm (27 x 54 in) |
EU | Often 60 x 120 cm, but check specific brands |
The CPSC crib mattress FAQs point out that while U.S. sizes are heavily regulated, global sizes are a bit looser — so if you’re mixing brands or shopping internationally, measure twice.
Honestly? Cot mattress sizing feels like it should be simpler than it is. But once you lock in the right fit, it’s one less thing to worry about at 3 a.m. when you’re half-asleep and trying to soothe a squirmy baby. And that’s the goal, right? Just one less thing.
Why Cot Mattress Dimensions Matter
Safety Implications of Incorrect Dimensions
Honestly, this one’s easy to overlook — especially if you’re piecing together nursery stuff late at night. But the fit of the mattress really does matter, and not just for aesthetics.
Here’s a quick gut-check list for what a safe cot mattress fit should look like:
- No more than a two-finger gap between the mattress and the cot frame — that’s the AAP’s benchmark for avoiding suffocation or entrapment (AAP safe sleep guidelines).
- Mattress should be firm and flat, not squishy or saggy in the middle.
- Check all four edges — sometimes it fits snug on one side but leaves a gap elsewhere.
- The mattress should not leave gaps at the head or foot of the cot.
- If you’re reusing a mattress or using one that didn’t come with the cot, double-check sizing. Seriously — it only takes a minute.
If you’re deep-diving on safety, this piece on how to keep baby safe in the crib is solid and grounded in real guidance.
Regulatory Standards for Cot Mattresses
So here’s the thing — the rules aren’t just there to be annoying. They’re there because babies don’t just lie still and sleep like Pinterest says. They roll, scoot, wedge themselves in corners. And if the mattress doesn’t fit right, that’s when stuff can go wrong.
The CPSC crib mattress regulations lay it out: crib (and cot) mattresses need to be no more than 6 inches thick, with strict dimension requirements to make sure there’s no room for entrapment (CPSC crib mattress regulations). That’s why size isn’t just about comfort — it’s a safety spec.
If you’re in the process of crib shopping or just trying to double-check what’s already in your nursery, this deeper guide on baby crib safety standards breaks it down in plain English. Worth a skim.
Choosing the Right Cot Mattress Size
Full-Size vs. Mini Cot Mattresses
This is one of those things you don’t think about until you’re staring at a box and wondering why the mattress doesn’t fit.
Mattress Type | Common Size (inches) | Notes |
Full-Size Cot | ~23.6 x 47.2 | Common in UK (60 x 120 cm) |
Mini Cot | ~24 x 38 | Used for smaller spaces or travel — see mini cot mattress size chart |
Twin Bed (for later) | 38 x 75 | Not compatible with cots, but worth knowing for the next stage |
If you’re thinking about space-saving setups, here’s a helpful post on whether mini cribs are a good idea — there’s more flexibility than you’d expect.
And if you’re hoping to get more than a year or two out of your setup, these cribs that grow with baby are actually kind of brilliant. Some even go from newborn to preschooler with just a few hardware swaps.
Toddler Bed and Cot Mattress Compatibility
So — is a toddler mattress the same size as a cot? Sometimes. If you’re using a cot bed (the kind that converts), then yeah, your mattress might carry over just fine.
But standard cot mattresses (like 60 x 120 cm) are usually too small for most toddler beds. Cot beds are closer to 70 x 140 cm. It really depends on the crib model.
More thoughts on that here if you’re in that in-between stage: will a crib mattress fit a toddler bed?
Also, worth checking out these top-rated convertible cribs if you’re starting fresh.
Travel and Portable Cot Mattress Sizes
Honestly, the world of travel cots is its own beast. Sizes are all over the place — and that’s what makes it tricky.
Here are a few travel cot mattress dimensions that show up a lot:
- 25 x 37 inches (for compact travel cots)
- 27 x 39 inches (standard for some foldable frames)
- 28 x 75 inches (larger portable cribs — rare but out there)
Key thing? You can’t really guess or improvise this — portable cot mattress size needs to match the model. Some brands have proprietary dimensions, so always check the label or the manual.
The CPSC has a bit on this too — under their broader guidance on durable infant products. Might help if you’re looking at secondhand gear or planning to travel with a young baby.
Also: if you’re wondering whether travel cribs are actually safe — they are, as long as everything fits right. This piece on are travel cribs safe lays it out well.
Common Cot Mattress Variants and Alternatives
Foam vs. Innerspring Cot Mattresses
Choosing between foam and innerspring mattresses? Here’s a quick breakdown.
Foam Mattresses
- ✅ Often lighter and easier to move (especially helpful when changing sheets)
- ✅ Can be more affordable
- ✅ Firmer options available — good for safe infant sleep
- ⚠️ Some lower-quality models may sag over time
- ⚠️ Check for safety certifications like the CertiPUR-US certification — it means the foam is free of things like formaldehyde and heavy metals
Innerspring Mattresses
- ✅ Usually more breathable — the coils allow better airflow
- ✅ May feel sturdier (especially helpful as your baby grows)
- ⚠️ Heavier to lift or move
- ⚠️ Often pricier
If you’re shopping, this list of safe crib mattress options includes both types that meet safety and durability standards.
Breathable and Organic Cot Mattresses
There’s a lot of buzz around breathable and organic mattresses — and some of it’s justified.
Breathable designs can help with airflow, which might ease some parents’ concerns around overheating or rebreathing risks. Just keep in mind: breathable doesn’t mean safer unless the mattress still fits snugly. A mattress that breathes but leaves gaps around the edge? Still a hazard.
Organic options go a step further. Many skip potentially harmful chemicals like PVC, flame retardants, or polyurethane foam. According to the Ecology Center’s mattress study, organic picks tend to reduce chemical exposure overall.
Still, materials vary widely. Cotton, wool, natural latex — each has trade-offs in firmness, breathability, and cost. For more thoughts on this (and how to tell if a “breathable” claim holds up), see this guide: Are crib mattresses breathable?
If you’re designing a whole nursery around natural or non-toxic materials, this piece may help: Designing a baby nursery
How to Measure and Fit a Cot Mattress
Step-by-Step Guide to Measuring
Getting the fit right is more important than the material, honestly. Here’s how to measure properly:
- Measure the interior of the cot — not the mattress. Use a tape measure to check the length, width, and depth.
- Convert to centimeters or inches, depending on what the mattress brand uses. (Common UK size: 60 x 120 cm)
- Check mattress specs before buying. The mattress should be just under the interior size — no more than 1 cm (or about a half-inch) smaller on any side.
- Mind the depth. The CPSC crib mattress FAQs say no more than 6 inches thick — any thicker, and it might sit too high or compromise side rail safety.
- Measure again after setup. Sometimes the mattress compresses during shipping — you want to be sure it expands fully before judging the fit.
Ensuring a Snug Fit
Here’s a quick tip box for fit checking:
➡️ Use the “two-finger test.” You shouldn’t be able to fit more than two adult fingers between the mattress edge and cot wall.
➡️ No shifting. Press down in the corners — the mattress should stay in place.
➡️ Re-check after a few weeks. Some mattresses settle or shift over time, especially foam ones.
According to the AAP safe sleep guidelines, that tight fit is key to reducing suffocation and entrapment risks.
Want a fuller look at how to keep your baby safe while sleeping? Start here: how to keep baby safe in the crib
Conclusion: What Actually Matters When Picking a Cot Mattress
Key Takeaways
- A snug fit isn’t optional — it’s the baseline for safe sleep. No gaps. No guesswork.
- Check both mattress dimensions and cot interior size. Trust your measuring tape.
- Foam vs. innerspring? Breathability? Go with what fits your priorities (and your cot).
- Certifications like CertiPUR-US can offer peace of mind, but nothing replaces a firm, snug mattress.
- Always double-check thickness limits and safety rules from sources like the CPSC crib mattress regulations and AAP safe sleep guidelines.
If you’re still piecing together the whole nursery puzzle, the ultimate crib buying guide lays it all out — types, sizes, safety checks, and what to skip.
And if you’re ready to browse, here’s a shortlist of highly recommended baby cribs that play nicely with standard-size mattresses.
References
- CPSC crib mattress regulations
- AAP safe sleep guidelines
- Federal Register crib mattress standard
- CertiPUR-US certification
- Ecology Center mattress study
- CPSC crib mattress FAQs
- CPSC durable infant products guidance
Related Posts
- how to choose the best crib mattress
- baby crib safety standards
- are crib mattresses universal
- will a crib mattress fit a toddler bed
- are mini cribs a good idea
- how to keep baby safe in the crib
- ultimate crib buying guide
FAQs
What is the size of a cot mattress?
Standard cot mattress sizes vary depending on region. In the UK, the typical size is 60 x 120 cm. In Australia, you’ll often see 68.5 x 137 cm. U.S. crib mattresses are usually about 28 x 52 inches (71 x 132 cm), which are often used interchangeably with the term “cot mattress” in American contexts.
Region | Standard Cot Mattress Size |
UK | 60 x 120 cm |
Australia | 68.5 x 137 cm |
USA (Crib) | 71 x 132 cm (28 x 52 in) |
For safety, the mattress should fit snugly with no more than a two-finger gap around the edges — this helps prevent entrapment risks. You can find more details in the CPSC crib mattress regulations.
Quick tip: measure the inside of your cot (not the mattress!) and compare it to the product specs before buying. Here’s a helpful guide on what are the dimensions of a crib mattress.
See some safe crib mattress options.
Are cot bed mattresses the same size?
Not exactly — cot bed mattresses are typically larger than standard cot mattresses.
Mattress Type | Common Size | Notes |
Cot Mattress | 60 x 120 cm | Fits most standard cots |
Cot Bed Mattress | 70 x 140 cm | Designed for larger or convertible cots |
Cot beds often convert into toddler beds, so the mattress needs to match both stages. The CPSC crib mattress FAQs suggest always checking with the manufacturer for proper sizing.
One parent told us they moved to a cot bed mattress around 18 months — the extra room gave their kid more space to roll around during toddler sleep regressions.
Helpful link: will a crib mattress fit a toddler bed, top-rated convertible cribs
How to measure cot mattress size?
- Measure the interior length and width of your cot — wall to wall.
- Measure the depth from the cot base (or slats) to the top of the side rail.
- Compare these numbers to your mattress label.
- Make sure there’s less than a 20 mm (or 0.8 in) gap on each side.
- Check height against safety rails (especially if the base has multiple height settings).
Checklist for a good fit:
- Less than 2-finger gap around edges
- Mattress sits flat without bunching
- No more than 6 inches thick
The CPSC crib mattress FAQs explain these points in more depth. Real talk? One mom told us she used a rolled-up towel to mock-measure mattress space before buying. Worked like a charm.
Also see: how to keep baby safe in the crib
How should a cot mattress fit?
Quick tip box:
- Do the two-finger test — you shouldn’t be able to fit more than two adult fingers between the mattress and the cot frame.
- Check all four sides for gaps.
- Press the mattress corners — they should bounce back but stay firm.
- Look for snug sheet fit with no loose fabric.
Why it matters: A too-small mattress can leave gaps where baby’s limbs (or head) could get trapped. That’s why the AAP safe sleep guidelines stress fit as a key part of sleep safety.
One parent told us they sleep better knowing their cot mattress doesn’t wiggle at all. Makes sense.
Also see: how to keep baby safe in the crib
Is a toddler mattress the same size as a cot?
Short answer? Not always.
Standard cot mattresses (60 x 120 cm) won’t fit cot beds or toddler beds that use 70 x 140 cm mattresses. Here’s a breakdown:
Mattress Type | Common Size | Fits In… |
Cot Mattress | 60 x 120 cm | Standard baby cots |
Cot Bed/Toddler Mattress | 70 x 140 cm | Convertible cots, toddler beds |
The CPSC crib mattress FAQs recommend checking for exact size specs before transitioning.
See related: will a crib mattress fit a toddler bed • cribs that grow with baby
Are cot mattresses universal?
Nope — not quite.
Cot mattress sizes vary by country and cot model. Here’s a look:
Mattress Label | Common Size | Region / Fit |
Cot Mattress (UK) | 60 x 120 cm | Standard cots in UK |
Cot Bed Mattress | 70 x 140 cm | Convertible cots, toddler beds |
Crib Mattress (USA) | 71 x 132 cm (28 x 52 in) | U.S. full-size cribs |
So, always double-check your cot’s interior dimensions. The CPSC crib mattress FAQs can help decode the sizing.
One parent shared they almost bought a mattress that was 2 inches too short — and only caught it by doing a tape-measure check.
Related reads: are crib mattresses universal • safe crib mattress options