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How Long Does A Memory Foam Mattress Take To Expand?

Our experts explain exactly how long your mattress should take to expand.

Buying a new mattress can be an exciting time – dreaming about how amazing your first sleep will be as you sink into the incredible softness of your new memory foam mattress – when all of a sudden you realise your mattress looks a little… flat. If you’re wondering how long a memory foam mattress takes to expand, we’ve provided our expert knowledge to help you figure it out.

We’ll take you through how long a memory foam mattress takes to expand, how to get it to expand properly, and cover any issues you may have with your mattress not expanding correctly or taking too long to expand. Keep reading to get one step closer to that ideal night’s sleep!

A rolled and packaged memory foam mattress on wooden floor.

How long does a memory foam mattress take to expand?

Most standard memory foam mattresses will take around 4-6 hours to expand up to 90%, and then it could take another 24-72 hours for it to expand to its full capacity. We recommend not sleeping on it before those 24 hours have finished because we want to ensure you have 100% satisfaction with the product you buy.

4-6 hours
to expand up to 90%
24-72 hours
to expand 100%

However, not waiting the full 24-hour period won’t affect your bed too much – you might just not have the most comfortable night's sleep possible with your new mattress that first night! The wait time is also recommended because your mattress will let off some chemicals when it comes out of the box.

These chemicals are not generally dangerous, but they can be irritating for people with asthma or breathing problems – something we’ve covered extensively in our guide to best sleeping positions for breathing problems! These chemicals can also give off a strange odour - but don't worry, the smell will go quickly.

Sometimes, it can take a little longer than a day for your memory foam mattress to expand. Some of the reasons why your bed might be taking longer to expand include:

  • Your bedroom has a low temperature – memory foam is temperature sensitive and will grow best in an area that has a warmer temperature. This is because heat improves the viscosity of the foam, making it easier to mould (like your body heat when you lie on it at night) so it will go firmer in the cold.
  • The memory foam mattress or bed topper has a high density or is particularly thick – the denser or firmer your mattress is, the longer it will take to expand. Check out our Memory Foam Mattress Buying Guide for more information on the different thicknesses you could try.
  • You don’t remove your mattress from the shipping box and packaging for a long time – your mattress will be deflated and folded when it’s sent to you, so it's best to unpack it immediately when you receive it to let it unfold and expand quicker.

How to get memory foam to expand

So, you know how long it will take for your mattress to expand, but how do you ensure that it’s got the best conditions to expand as quickly as possible? Most mattresses will come with instructions about how to set them up, but here are the steps you should take to make sure your memory foam mattress can expand properly:

  1. Remove the mattress from all the packaging it came in
  2. Bring your mattress into your bedroom or large open space where it can lie on the floor
  3. Keep the room warm – memory foam responds best to heat, but not too much heat! Don’t try to use the hairdryer on it, or leave it too close to a portable heater, as mattresses can be flammable
  4. Carefully separate the layers of memory foam by pulling gently
  5. Once it has expanded, place it on your bed and add your bedding before drifting off into dreamland
Memory foam mattress laying flat on the floor as it expands quickly.

How to make memory foam expand faster

If your mattress is taking a little longer to expand (or you’d like to sleep on it that night), then you’ll want to find some nifty tricks to speed up the process a little. Unfortunately, the top trick is to wait the full amount of time, but there are some things you can do to make the process a little speedier:

  • Roll on your mattress for 10-30 minutes – your body heat and movement will help the foam to expand quicker.
  • Keep the room it is in above 20°C – keeping the room toasty will help the foam to expand quicker, and it will mean you’re perfectly toasty by bedtime too.
  • Ensure that it has time to expand on a hard surface – letting your memory foam mattress expand on the floor is our top recommendation because it encourages expansion.
keep your room at this temperature for faster expansion

Why is my memory foam mattress not expanding?

You can tell if your bed has fully expanded because it will have reached its full measured size, and the corners will have filled out completely. If your memory foam mattress hasn’t expanded fully in five to seven days, then the chances are that you have a defective mattress on your hands. Fortunately, this is rare, but you will want to contact the manufacturer to get you sorted with either a replacement or a refund.

A memory foam mattress is one of the ultimate options for cushion and comfort, and they suit a wide range of sleepers, so purchasing one for yourself and letting it expand fully will lead to the dreamiest night's sleep you could imagine!

Why not check out our range of mattresses, from single to king-size, or use our Mattress Finder to discover the bed that will work best for you? Sweet dreams!

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