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13 October 2020

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
Alison Potter

What is a good cot mattress? You want one that's going to help your baby to a good and 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.

But there are other questions you also need to think about when deciding which cot mattress to buy.

How much do I need to spend to get a good mattress?

A cot mattress can cost anything from £30 to £300. A premium cot bed mattress will set you back £200 or more. But price and quality don't necessarily go hand in hand. We have tested some reasonably priced cot mattresses that score higher in our tests than top-of-the-range ones. 

To see which mattresses excel in our stringent safety and durability tests, compare our cot mattress reviews

What is the best cot mattress for baby?

Whether buying a cot mattress or a cot bed mattress, you want a firm and flat mattress protected by a waterproof cover to help keep the mattress clean and dry. You can assess for 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.

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. We measure body support before putting it through a durability test that simulates 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 is the size of a cot mattress?

While cot mattresses and cot bed mattresses can come in many shapes and sizes, there are some general sizes for each you will see while shopping. A cot mattress is typically 120 x 60cm in size, cot bed mattresses are commonly 140 x 70cm. 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 you. 

How thick should a cot mattress be?

We recommend that your baby's cot mattress be at least 10cm thick. Your baby's weight will be concentrated on a small area on his or her cot mattress and you don't want their body sagging through the mattress and hitting the cot bed beneath. Your baby needs a mattress that provides good support and won't sag. You want a mattress that feels firm rather than soft. To compare firmness, squeeze at the edges and in the centre. 

What are the different types of 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.

In our tests we check every mattress for its support and durability, so you can cut through all the confusing advertising jargon and find the mattress that will continue to give your baby a comfortable and supportive night's sleep as he or she grows. 

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

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.

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.

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. 

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.

Find out more about cot mattress safety.

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