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26 February 2021

Which cot mattress should you buy?

What is a good cot mattress? How thick should it be? What cot mattress is best for baby? How should it fit? Get the answers to these questions and more.
How to buy the best cot mattress
Sam Morris

What makes a good cot mattress? 

You want one that's going to help your baby have a safe night's sleep, keep them comfortable, cope with the inevitable leaks that will come its way and last for as long as you need it.

We’ll help break down what you need to look out for, in the pursuit of buying the best cot mattress.

Discover our Best Buy cot mattresses to give your little one the best night's sleep

The best cot mattresses 2021

Our robust and impartial lab tests have uncovered the very best cot mattresses on the market.

Below, we’ve selected our top cot mattresses picks. All of them have performed well in our body support, durability, and safety tests, so you can be sure you are buying the best.

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Best Buy

We were very impressed with this cot mattress. It is firm and durable, providing the body support needed for your growing child. Not only this, but it is well ventilated and easy to clean. Scoring highly across our test results, we highly recommend this cot mattress.

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Best Buy

This high scoring foam cot mattress is well priced, comes with two covers and is reversible. It scored high in our durability and body support tests - being it should last until your child is ready to move to a junior bed. On top of this it is also reversible! This cot mattress provides excellent value for money.

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Best Buy

This foam cot mattress is particularly, and it offers good body support to babies and toddlers. It's very easy to clean, though it's worth noting that it loses firmness over time, so it's not ideal to reuse with a second child. With it's reasonable price and features, this cot mattress is a great option to consider if purchasing from new.

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Best Buy

This cot mattress excels in terms of firmness and body support. It's durable, meaning it will last for at least three years with only a minimal change in height and firmness. The cover is easy to remove and clean, although you might want to invest in an extra waterproof cover. This cot mattress performed well across our testing.

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Best Buy

There’s plenty to like about the Ikea Drömmande cot mattress, not least the fact that it’s firm, supportive and held up well in our durability tests. There’s also a handle to help you move it, and a removable washable cover to keep it fresh. Scoring highly across our tests, the Ikea Drömmandecot mattress is definitely one to consider.

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Table updated 24 February 2021   

The best cot mattress brands

As well as our tough tests, we also ask parents how happy they are with their chosen cot mattress brand, so we can give you some insight into the best brands out there and the ones to avoid.

As you can see, our tests have uncovered a sizeable difference in the best and worst cot mattress brands, and the feedback from parents is varied too.

We asked 1,598 parents to tell us which brand of cot mattress they owned, and how satisfied they are with that brand. We also asked them whether they would recommend it to a friend.

From these responses we’ve compiled an overall customer score and star ratings. Have a look at the results for the biggest cot mattress brands below.

Only logged-in Which? members can view the hidden results in the table below. If you're not yet a member, join Which? to get instant access.

Babystyle Ikea John Lewis Mamas & Papas Marks & Spencer Silentnight
Number of models tested 1 4 4 4 1 1
Which? test and customer scores

Table notes: Average test score based on results of models tested that are still available as of 1 February 2021. The customer score and rating are based on a Which? member survey of 1,598 parents conducted in March 2019.

What to look for when buying a cot mattress

When buying a cot mattress, you want a firm and flat mattress, with a waterproof cover to help keep the mattress clean and dry.

You can assess the firmness and flatness of the mattress by pressing your hand firmly into the centre and edges. There should be some resistance and it should bounce back immediately.

Also make sure it's in good condition and fits the cot or cot bed you're using it with.

We assess the support a cot mattress will provide for your baby. Our experts measure body support before putting it through a durability test that simulates two to three years of regular use.

We then measure the body support after these tests to see how your cot mattress will hold up, so you know the mattresses that are going to still be doing a great job of keeping your baby comfortable over time. 

What to know more about how we sort the wheat from the chaff? Learn more about how we test cot mattresses in our testing guide

Cot mattress FAQs

With so many things to consider when purchasing a cot mattress, it can be tricky to know where to start.

We’ve compiled and answered the most common cot mattress queries, so you can feel confident in your search for the best cot mattress.  

How much does a good cot mattress cost? 

The prices of cot mattresses range anywhere from about £30 to £300, with a premium cot bed mattress setting you back £200 or more.

But price and quality don't necessarily go hand in hand, with our cheapest Best Buy costing under £50, and our most expensive Don’t Buy over £200.

Quality and safety do not always go up with price, so it may be worth looking at performance before price when it comes to cot mattresses.

What is the standard cot mattress size in the UK?

140 x 70cm is the standard size of most UK cot beds, so you want to buy a cot bed mattress with these dimensions. This will ensure the mattress fits snugly into the frame, leaving no gaps around the edge of the mattress.

Another typical cot mattress size is 120 x 60cm. If you buy a cot that is smaller or larger than the norm, you can get mattresses specially made to fit your cot – but this is going to cost more.

How should a cot mattress fit?

You need to make sure your cot mattress fits your cot or cot bed frame snugly. A gap bigger than 3cm (or 1.2 inches) is a potential hazard for your baby. Your baby's arms, legs, or head could get trapped in a gap.  

Not all cot mattresses come in the same standard size, but your cot or cot bed should specify which size cot mattress it requires. 

If you have your heart set on a cot or cot bed that doesn’t work with a standard-size mattress you can get a custom-sized one made. However, this is going to cost more so keep that in mind.

How thick should a cot mattress be?

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

Your baby needs a mattress that provides good support and won't sag, so you need to buy a mattress that feels firm rather than soft. To compare firmness, squeeze at the edges and in the centre.

Which way up does a cot mattress go?  

Many cot mattresses (mainly of the spring and pocket spring varieties) are made to be reversible. Each side of the mattress will be specially designed to accommodate the needs of your rapidly growing baby.

That's because a cot mattress might be used for five or six years, during which time your baby will more than triple in weight. Because of this, manufacturers often design cot mattresses with one side specifically for babies and the other for toddlers or children.

Typically one side will have springs and foam designed to be sturdy, but gentle for your baby to sleep on for the first 12 months of his or her life. The reverse side will have sturdier material to cope with your growing toddler.

The mattress should clearly indicate which side is suitable for what age group. 

Take a look at our best cot mattresses to find those which come top in our tough tests

The different types of cot mattress

Foam vs spring? Spring vs pocket spring? Or natural?  We discuss the pros and cons below.

Foam cot mattress

Generally speaking, foam cot mattresses are the least expensive type of cot mattress. They are very simple – normally a piece of high-density foam with a wipe-clean, waterproof PVC cover. Some will come with two sides: a cotton side and a wipe-clean side. 

Some foam mattresses have ventilation holes, but these aren't necessary. You might also see hypoallergenic foam mattresses advertised. 

You'll see the type and strength of foam referred to in a number of different ways: 'Highly resilient', 'dent resistant', 'combustion modified'. You could also see a CMHR (combustion modified high resilient) foam number quoted. In theory the higher the number the firmer the mattress support is supposed to be. 

Foam cot mattress pros 

  • Generally easy to keep clean. 
  • Good value for money. 
  • Can provide good support and resistance to denting. 
  • Foam is usually the lightest of the three main mattress types, so will be easy for you to move or flip.

Foam cot mattress cons 

  • Some parents don't like the idea of the basic, all PVC-covered mattress because of concerns about clamminess. 
  • Foam mattresses with ventilation holes (designed to help keep your baby cool) can be more effort to keep clean if your baby is a dribbler or is often sick, because residue can gather in the holes and mesh.
  • Bear in mind that thin foam, in particular, can lose its shape and dent easily.

Spring or pocket spring cot mattress

A simple spring mattress is made of springs secured into a rigid frame. These are then surrounded by layers of foam and fabric. 

Pocket spring mattresses are the most expensive type of cot mattress. These are made of coiled springs, each sewn into their own individual pocket. 

Unlike a regular spring mattress, each spring in a pocket spring mattress can move independently of the others, so the mattress is deemed to be more comfortable and give better support. These springs are, like regular spring mattresses, covered by layers of foam and fabric. 

Spring cot mattresses often have a cotton cover on one side and wipe-clean material on the other side. 

Spring cot mattress pros 

  • Many parents like the familiarity of a traditional spring mattress. 
  • The wipe-clean side is the recommended surface for your baby to sleep on because of the practical advantages, but you can flip it over onto the cotton side if you prefer – eg, if it's hot and your baby feels clammy. 

Spring cot mattress cons

  • More expensive than foam mattresses. Pocket spring cot mattresses are also more expensive than the spring types.
  • The cotton side may be preferred for comfort but can be more difficult to keep clean (unless you buy a mattress with a removable panel).

Coir or natural fibre cot mattress 

These have a core of coconut fibre with other layers of different materials. The fibres are coated in latex for strength and protection, and the natural fibre filling helps air circulate through the mattress. These mattresses are available with a wipe-clean covering. 


  • One of the firmest types of mattress. 
  • Tend to last longer because they hold their shape well, so could be a sensible buy if you want to use it for more than one child. 


  • Less widely available than foam or spring interior. 
  • Can be more expensive than the alternatives.

Hollow frame (PurFlo) cot mattress

This type of hollow, frame mattress is only made by PurFlo. It's advertised as the only fully breathable, fully washable cot mattress. It's basically a mesh covered frame. 


  • Whole mattress, excluding the frame, is washable.
  • Provides good air circulation for your baby as it's hollow.


  • More expensive than most other cot mattresses.
  • Is 15cm deep so you'll need to keep your cot or cot bed on its lowest setting to ensure you have a decent enough gap from the mattress to the top of the cot or cot bed's rail.
  • Parents divided on how comfy their babies find it. 

Hypoallergenic cot mattress

These have a quilted top layer that can be easily detached from the body of the mattress, so you can wash it at 60°C to kill any dust mites that may cause allergies. 


  • Easy to keep clean.


  • May be more expensive than other kinds of mattress.

Find more helpful guidance in our bedding safety and safe sleeping advice guides

Should you buy an organic or natural cot mattress?  

Maybe you like the idea of putting your baby to sleep on an organic or natural mattress.

Manufacturers of these claim to use all natural materials – no chemicals or synthetic materials.

Organic is commonly understood to mean that the materials would not have been subjected to chemicals or pesticides in any stage of production.

But manufacturers can use the terms ‘natural’ and ‘organic’ on products without needing any sort of certification. There are legal requirements for the labelling of organic foods, but not these products.

That said, there are many organisations that offer certification for natural and organic claims. The Little Green Sheep, for example, certifies some of its materials through the Global Organic Textile Standard (GOTS). It's down to the certification body, such as GOTS, to make sure the suppliers of materials comply with its guidelines for organic.  

Our advice is to make sure you read the fine print carefully, as the term organic or natural can be used to market a whole product when, in fact, only some of the ingredients or materials have been certified as organic. Or, in many cases, the terms are used without the added security of a certification. In this case you have to trust that the manufacturer is honest about its claims.

What about a travel cot mattress?

A travel cot mattress should be no more than 10cm thick and you should expect the mattress in a crib or Moses basket to be no more than 5cm thick. These thicknesses are specified in BS 1877:Part 10:1997, the safety regulations that govern cot mattresses.

View all Cot mattresses