Best cot mattresses: expert picks from our safety tests

You need your cot mattress to be able to cope with inevitable accidents, and you need it to last until your child is ready for their first bed. We've found Don't Buy cot mattresses that are too soft, not breathable and that won't last long enough.

We've tested dozens of cot mattresses over the years from brands including Ikea, John Lewis, Mamas & Papas and Silentnight. Our lab tests assess body support, durability and hazards, to make sure the cot mattress will provide a comfortable, supportive and safe sleeping surface for your little one. 

Safety is a crucial part of our assessments and all models are tested to the latest version of the cot mattress safety standard (2021). The cot mattresses are for a standard UK cot bed and measure 140 x 70cm.

The best cot mattresses from our tests

The biggest brands and the most popular 10 cot mattress are listed below.

Only logged-in Which? members can view the cot mattress test results below. 

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The cot mattresses we tested

A selection of the cot mattresses we tested are listed in alphabetical order below.

Only logged-in Which? members can view the cot mattress test results. 

Join Which? to get instant access to our test results and Best Buy recommendations.

Cuggl Hypoallergenic Sprung Mattress

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Available from: Argos (£50)

Most recently tested December 2021

Type Bonnell spring with foam

Need to know Weighs 4.3kg, 140.4 x 70 x 10.9cm (LxWxD), hard firmness, removable cover

Ikea Drömmande

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Available from: Ikea (£99)

Most recently tested August 2022

Type Pocket spring with coir and latex

Need to know Weighs 7.8kg, 140.1 x 70.1 x 10.7cm (LxWxD), hard firmness, removable cover

Ikea Krummelur

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Available from: Ikea (£59)

Most recently tested February 2024

Type Foam

Need to know Weighs 3.3kg, 142.4 x 71.93 x 8.6cm (LxWxD), very hard firmness, removable cover

Ikea Skönast

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Available from: Ikea (£75)

Most recently tested March 2024

Type Highly resilient polyurethane foam (cold foam)

Need to know Weighs 3.2kg, 140.5 x 70.9 x 7.8cm (LxWxD), hard firmness, removable cover

John Lewis Premium Fibre Cotbed Mattress

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Available from: John Lewis (£68)

Most recently tested December 2021

Type Fibre

Need to know Weighs 3.5kg, 140.9cm x 70.7 x 11.1cm (LxWxD), very hard firmness, removable cover

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Kub Charm Eco Luxury Pocket Spring Cot Bed Mattress

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Available from: John Lewis (£160)

Most recently tested December 2022

Type Pocket spring

Need to know Weighs 4.4kg, 140.8 x 71.4 x 10.8cm (LxWxD), medium firmness, removable cover

Silentnight Safe Nights Snuggle Breathable Mattress

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Most recently tested February 2024

Type Foam

Need to know Weighs 3.1kg, 141.3 x 71.5 x 9.6cm (LxWxD), very hard, removable cover

Silentnight Safe Nights Twinkle Breathable Mattress

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Type Pocket spring

Need to know Weighs 4.9kg, 141.9 x 72.5 x 10.9cm (LxWxD), hard firmness, removable cover

Silver Cross Superior Cot Mattress

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Most recently tested November 2018

Type Pocket spring and foam

Need to know Weight 5.9kg, 140.5 x 70 x 12cm (LxWxD), medium firmness, removable cover, reversible

Simba Hybrid Cot Bed Mattress

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Most recently tested February 2024

Type Hybrid

Need to know Weighs 5.2kg, 141.5cm x 71.6 x 11.1cm (LxWxD), very hard firmness, removable cover, reversible

More cot mattresses from our tests

Here’s how the rest of the cot mattresses from our tests measured up, listed in alphabetical order.

How we test cot mattresses

• How well does the mattress support my baby? We use a 12kg and a 21kg dummy to measure the level of body support as your child grows.  
• Is the cot mattress firm enough? We test each cot mattress to see how firm it is when it's new and how this compares with other mattresses. It's crucial your baby lies on a flat, firm mattress. 
• How durable is it? Our tests put each cot mattress through the equivalent of roughly two to three years of use. We then record any changes to the mattress, including damage. A good mattress will be able to withstand our durability test and retain its firmness throughout. It should also retain its height.
• How well does the mattress move moisture away from your baby? It's important that your baby doesn’t sleep on a damp cot mattress, and we test each mattress to see how easily moisture moves away from the outer layers. We've found that some are very good at doing this, while others allow liquids to sit on the surface.
• Does the mattress have good airflow? We use special equipment to check the airflow through the mattress. This is to assess how breathable it is, as it’s important for fresh air to circulate around your baby’s face, and to see whether the mattress draws away body warmth effectively so your baby doesn’t overheat.
• How easy will it be to clean? If it has a removable cover, we'll check how easy this is to get on and off. We also assess how the mattress cover fares after several washes. If a cover shrinks, then it could potentially compress and reduce the size of the mattress and cause unsafe gaps.

We regularly revisit the cot mattresses on sale to see if there are any more popular brands that need testing, and when we find them we do. 

Find out more about how Which? is not influenced by product manufacturers or retailers and how your support helps us to stay editorially independent.

Don’t Buy cot mattresses

Our safety tests replicate those in the current cot mattress safety standard, BS EN 16890:2017 + A1:2021 and they uncover what we consider to be the best and the worst. 

If a product performs so poorly that we think you should avoid it, we call it a Don't Buy. We've tested 14 cot mattresses that we've named Don't Buys, based on their performance under our independent safety tests.

There are three serious safety issues we commonly see:

1. Suffocation risk - A baby's face can sink into the mattress if they roll onto their front and the top layers of the mattress are too soft, posing a suffocation danger. This is a serious concern for younger babies (roughly aged 4-12 weeks), when they begin to roll over from their back to their front. Rolling from front to back requires more strength, and some babies may not master this skill until they reach around six months old. We check the firmness of every mattress when new and also after our durability tests, to see if it poses a suffocation risk. 

2. Entrapment risk - If there's a gap because the mattress doesn't fit the bed frame properly, there's a risk that a baby or young child can trap an arm or a leg. If they get caught while lying face down, it's a suffocation hazard. That's why it's essential the mattress is the correct dimensions when new (140x70cm). Another issue is the mattress cover shrinking after being washed, which compresses the mattress when the cover is put back on, and this again can cause unsafe gaps where a baby could get trapped.

3. Choking hazard - We frequently see zip pulls come away too easily, and they're small enough to be easily swallowed and block a child's airway. Similarly, if they can access the filling of the mattress, this is another choking risk 

Go to our Don't Buy cot mattresses to see which cot mattresses failed our tests and the types of safety issue to look out for. 

What is the standard cot mattress size in the UK? 

The standard dimensions of mattresses that fit most UK cot beds is 140 x 70cm and this is the size we test. Another typical mattress option is 120 x 60cm, but that's typically just for cots that don't convert to a toddler bed.

Whatever mattress size you go for, you need to make sure the mattress fits your cot or cot bed frame snugly. A gap bigger than 3cm (1.2in) is a potential hazard for your baby as their arms or legs could get trapped in the gap.

We recommend that your baby's cot mattress is at least 10cm thick. Your baby’s weight will be concentrated on a small area of the mattress, and you don't want their body sagging through and hitting the base underneath.

Should you buy a second-hand cot mattress?

We don't recommend buying or using a second-hand cot mattress. Where possible, always buy new. This is also the advice of baby sleep charity The Lullaby Trust.

Our tests have found that cot mattresses can lose more than 25% of their firmness in just a few years of use. This means that using a second-hand or hand-me-down cot mattress may not provide the firm support all babies need, and could increase the risk of suffocation or smothering.

When we surveyed 1,878 parents in February 2021, 61% said they used a new cot mattress but 39% went for a second-hand cot mattress.

Around half of parents with a new cot mattress said they had issues with it, but this increased to around nine in 10 parents when the mattress was second-hand. 

A quarter of second-hand cot mattress owners reported indentations forming in the mattress or sagging. A mattress that isn't firm and flat won't provide enough support for your baby, and it just isn't worth the risk to their safety.

Second-hand cot mattress checklist

If you plan to reuse a cot mattress with a subsequent child, or if you've bought a second-hand mattress, use our checklist below to make sure it's fit for use:

1. Check it's still firm and lies flat, with no holes or tears When you press down, there should be resistance and the mattress should spring back immediately after you remove your hand.
2. Look for sagging If any sections are too soft, the cot mattress won't provide enough support for your child. This is especially dangerous if your baby ends up face down in the sagging area, as it could be a suffocation risk.
3. Make sure it fits the cot frame with no gaps around the edges Take a tape measure and check the length and width of the mattress at multiple places on the mattress. If there are any gaps larger than 3cm when it's in the bed, then that could be an entrapment risk.
4. Clean and air-dry thoroughly before using Make sure it's free of dirt and bacteria before your little one sleeps on it. 
5. Put on a waterproof cover This will reduce the risk of unhealthy bacteria lurking in the mattress. Potentially, you could buy a new outer cover that can be washed at 60ºC.

Baby sleep positioners, pods and nests

Baby sleep positioners, cushioned sleeping pods and baby nests are popular with parents, but we have concerns as these products don't provide a flat, safe sleeping surface. They pose a risk of suffocation if your baby rolls onto their front, so they should never be used without supervision. 

There were 13 infant deaths in the US between 1997 and 2011 linked to the use of sleep positioners. The Food and Drug Administration (FDA) in the US released a statement warning about these items, which are also known as 'anti-roll' products, warning parents not to buy or use them.

Which? doesn't review these products, and current safe-sleeping advice from The Lullaby Trust is to keep cots clear of pillows, toys, bumpers and sleep positioners, because the evidence shows that this reduces the risk of sudden infant death syndrome (SIDS).