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24 June 2021

How to buy the best mattress

We explain how to find the best mattress without paying thousands of pounds.
Ben Slater
A pocket sprung mattress

Do you want a good night’s sleep? Deciding which type of mattress to buy is only part of the story. 

Whether you prefer a pocket sprung or a memory foam mattress, our tests have found big differences between the best and worst of each mattress 'type'.

Make the wrong choice and you risk being lumbered with a needlessly expensive mattress that's uncomfortable, unsupportive and unable to stand the test of time without sagging and softening. 

Thankfully, we've explained everything you need to know below to ensure you get the right mattress. 

Video: how to buy the best mattress

Watch our video to help you pick the perfect mattress for your sleeping position, body shape and bedroom.

Types of mattress

Pocket sprung, latex, hybrid and memory foam mattresses have all impressed in our tough tests, so the type of mattress you choose really comes down to personal preference and budget.

Pocket-sprung mattresses

If you want a traditional mattress with a natural filling, such as wool, you'll want a pocket sprung mattress. 

With these, each spring is enclosed in its own fabric 'pocket' – each reacts to pressure from your body independently. However, these can be pricey and our tests show some can sag significantly over time.

Memory foam mattresses

Memory foam mattresses can be more durable and mould to your body shape but, in some cases, this can increase your body temperature and restrict your movement.

For more information about mattress types, see our guide to choosing the best type of mattress.

How much does a good mattress cost?

A new mattress can cost anywhere between £100 and several thousand, so whatever your budget there will be a mattress for you. Factors such as brand, size and the types of material used can all have a significant impact on cost.

But, as the graph below shows, our mattress tests have found you don’t need to spend a fortune to get a mattress that will support your spine and last for years. Take a look at our list of the best cheap mattresses.

Number of Best Buy mattresses by price

What are the best mattress brands?

Our April 2019 survey of more than 5,000 mattress owners revealed that three in 10 Which? members bought their current mattress because it's made by a brand they trust. If you're not sure what the best mattress brands are, we can help. 

Check out our guide to the best and worst mattress brands. This reveals what people think of the brand of mattress they own, including how comfortable their mattress is, and covers major brands such as Casper, Ikea, John Lewis, Sealy and Silentnight.

Soft vs firm mattresses

When it comes to firmness, the most important thing is to buy a mattress you find comfortable. 

Don't buy a mattress that's firmer than you'd like on the assumption that it will be more supportive. 

Time and again, our tests have shown you don't have to buy a firm mattress to get excellent and long-lasting support. 

Equally, don't assume that a firm mattress in one store will feel the same in other shops. 

Firmness is subjective and manufacturers describe the firmness of their mattresses in a range of ways. 

That's why we don't use terms such as soft and firm in our mattress reviews.

Instead, we objectively test mattress firmness on a scale of one to 10, where one is the firmest and 10 the softest, so you can easily compare the firmness of different mattresses.

To test mattress support for side-sleepers, we use a laser to measure the straightness of a person's spine, at five different points.

We also measure how supportive each mattress is for a range of different body sizes and sleeping positions, so if you prefer to sleep on your front, side or back - we've got you covered.

Use our mattress reviews to arm yourself with a shortlist of supportive mattresses to try out in store.

Best mattresses: features to look out for

As mattresses serve a single basic function – to help us sleep – they don't come overloaded with jazzy features. But there are still a few things to look out for.

  • Memory foam Similarly, just because a mattress contains memory foam doesn't make it a memory foam mattress. We only class a mattress as memory foam if it contains more than just a token layer of the body-moulding material. See all our memory foam mattress reviews or our round-up of the best memory foam mattresses for 2021.
  • One-sided As the name suggests, only one side of a one-sided mattress is designed to be slept on. Mattresses can be extremely heavy – the heaviest we've seen weighs more than 50kg – so you may be relieved not to feel obliged to flip it. You'll probably still need to rotate it from head to toe, though, so it's a good idea to check the ease of use rating in our mattress reviews.
  • Natural fillings Many pocket sprung mattresses also contain layers of synthetic fillings, such as foam. If you're keen to avoid these, look out for mattresses that specifically claim to be made using only natural materials. Look carefully at the claims though, some may only have a token layer of natural materials.

Try before you buy

Buying a mattress online may be cheaper and more convenient but, unless you’re buying a bed-in-a-box mattress (see below), it’s always best to try before you buy if you possibly can - and shops are open. 

When we asked Which? members about their experience of buying a mattress, more than a third of them told us they feel intimidated trying out a mattress in the shop. A good mattress shop shouldn't mind you doing this. See our guide on the best mattress shops.

When trying out a mattress in-store:

  • Wear comfortable clothing and remove your outdoor gear.
  • Lie on a mattress for at least 10 minutes, in positions you normally sleep in.
  • If the bed is for two, go with your partner. 
  • Don’t shop for beds when you’re tired, as all the mattresses will feel great.
  • Don't let sales assistants influence you – they can’t decide whether the mattress is comfortable for you.

If you’re buying a memory foam mattress, relax in one position, then move into another. Was it easy or did you struggle to move? If the latter, you might find the memory mattress will restrict your movement too much, especially in cold weather when the memory foam will be harder.

Buying a mattress online?

If you’re looking for a bargain mattress, one option is to try a few mattresses out in a shop, before going home to search for the best price online. 

That’s what 6% of Which? members did when they bought their last mattress, according to our recent October 2020 quick poll. 

Unsurprisingly, given the events of 2020, around 76% responded to say they'd bought online (without trying their mattress first). While 16% tried a mattress in-store before having it delivered to their house.

If you can't get out to the shops, as they are shut due to lockdowns and restrictions, here are our top tips for buying online

  • Research When you buy online you’re protected by consumer law. But do your research first – read our reviews and opt for a model that best fits your sleeping style. We have picks for front, side and back sleepers, people who fidget a lot, and those that tend to get too hot or cold.
  • Use trial nights offers Find out whether your chosen mattress has a trial period, how long this lasts and how you return it once the trial is up. Look for any hidden costs involved, and whether you have to return the mattresses back in the original packaging or not.
  • Know your rights If you change your mind, you’re entitled to a 14-day cooling-off period from the date you receive goods, meaning you can cancel your order at anytime from the moment you place your order up to 14 days from the date it arrives, and the seller is obliged to refund you.
  • Measure up Measure your bed frame’s base, especially if you’ve had it for a while. Dimensions can vary, so don’t rely on a new double mattress being exactly the same size as your old one. It’s worth getting your tape measure out to avoid a troublesome error.

Bed-in-a-box mattresses

These are mattresses that are bought online, vacuum-packed into a box and delivered direct to your door, and there are three reasons you should consider one:

  1. By cutting out the retailer and selling direct from manufacturer to consumer, many brands claim you’re getting a higher-quality mattress for less.
  2. Most online-only mattresses offer a sleep trial of at least 10 weeks. During this time you can try the mattress at home and send it back for a full refund if you don’t like it. In most cases, the manufacturer will collect the unwanted mattress from your house for free before recycling it or donating it to charity.
  3. We’re yet to test a bad one. More than half of the Best Buy mattresses we've uncovered can only be bought in a box.

See our list of the best bed-in-a-box mattresses.

Make sure your mattress fits your bed base

Manufacturers may encourage you to buy a mattress and bed base together, and this is a good idea if you’ve had your old base for many years.

If you buy the mattress and base separately, or are going to keep your old base, measure carefully to make sure they’re a good fit. Dimensions can vary so don’t rely on a new double mattress being exactly the same size as your old one.

Is your mattress going onto a slatted base? Make sure the slats are no more than 6cm wide or more than 4cm apart. This ensures sufficient ventilation, while preventing the mattress sagging through between the slats.

For more information, read our guide what bed size do you need for your mattress? 

Check the guarantee/warranty on your mattress

Make sure you know what your rights are if there's a problem with your mattress.

Most guarantees for mattresses will not cover gradual wear and tear, which leads to loss of support. So make sure you use our mattress reviews to pick out a durable mattress that will stand the test of time.

Before you buy your mattress, check whether there’s anything in particular, such as removing labels or using a base other than a recommended one, that would invalidate the guarantee.

Now you know what to look for, check our best mattress recommendations for a Best Buy that will support your spine and last for years.