How Long Does A Memory Foam Mattress Take To Expand?

Buying any type of new mattress can be an exciting time, especially if you’re investing in a top-of-the-range memory foam mattress!

From the moment you place your order, you’re probably already dreaming about how amazing your first sleep will be as you sink into the incredible softness of your new bed. But when it arrives, you might find your mattress looks a little… flat.

Fortunately, this flatness is totally normal for memory foam mattresses, but if you’re wondering how long a memory foam mattress takes to expand, we’ve provided our expert knowledge below to help you figure it out and put to bed any quality concerns you may have.

From notes on how long a memory foam mattress takes to expand to how to get it to expand properly, we’ve covered any issues you may have with your mattress not expanding correctly, including if it’s taking too long to expand.

Keep reading to get one step closer to that ideal night’s sleep as our experts explain exactly how long your mattress should take to expand!

How long does a memory foam mattress take to expand?

Most standard memory foam mattresses will start to expand as soon as they're unrolled, however, we recommend not sleeping on yours for the first 24 hours. This gives your new mattress time to expand properly, and you'll likely notice that your mattress is almost at 100% capacity once 72 hours have passed.

However, in some cases, it can take up to a couple of weeks for your mattress to expand to 100%, but this is nothing to worry about - after all, you'll be enjoying your new bed for years to come, so a little patience will be more than worth it.

How long to leave a mattress before sleeping on it?

As we’ve already mentioned, holding off sleeping on your new mattress for the first 24 hours is highly recommended, but not just because you want it to expand into shape. It’s also 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!

More to the point, these chemicals can also give off a strange odour which can be unpleasant to sleep with – but don't worry, with proper ventilation, these smells will dissipate quickly.

Why is my memory foam mattress not expanding quickly?

When it comes to the question of “How long does it take for a mattress to expand”, there can be many reasons for it to take longer than a day. Below are some reasons as to why it might be taking longer for your memory foam mattress to expand:

• Low bedroom temperatures – memory foam is a temperature-sensitive material and will grow best in warmer rooms. 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 and thus take longer to expand.
• High-density foam – the denser or firmer your mattress foam is, the longer it will take to expand. Check out our memory foam thickness and density guide for more information on the different thicknesses you could try and why this might lead to longer expansion times.
• Leaving it in the packaging – as you might expect, your memory foam mattress will be compressed, rolled up and boxed 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, otherwise you might find the foam has solidified.

How to get memory foam to expand properly

So, you know how long it will take for your new memory foam mattress to expand, but how do you ensure that it’s in the best condition to expand as quickly as possible?

Well, most mattresses will come with instructions about how to set them up, but here are some general steps you should take to make sure your memory foam mattress can expand properly from the moment you unpack it:

1. Remove your 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 and air properly.
3. Keep this room warm as memory foam responds best to heat, (but not too much heat). Let it settle and expand on its own, and don’t try to use the hairdryer on it or leave it too close to a portable heater where it could catch fire.
4. As it expands, you can carefully tug the layers of memory foam into shape by pulling on them gently.
5. Once it has expanded properly, place it on your bed and add your bedding before drifting off into dreamland.

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 we’ve no doubt that you’ll want to find some nifty tricks to speed up the process a little. Unfortunately, the top trick is to wait the recommended full amount of time before sleeping on it, 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 faster.
• Keep the room it’s in above 20°C, as 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 with as much air circulation as possible. If you have a spare slatted bed frame, place it on there to let as much air get inside your expanding memory foam mattress as possible.

Why is my memory foam mattress not expanding?

Once your mattress has been left to expand for a while, you’ll be able to tell if your bed has fully expanded because it will have reached its full measured size, and the corners will have filled out completely - check our bed size guide to compare.

However, if your memory foam mattress hasn’t expanded fully in five to seven days, then chances are you have a defective mattress on your hands. Fortunately, this is rare, but you’ll still want to contact the retailer or manufacturer to get sorted out with either a replacement or a refund.

You might find our guides to making a soft mattress firmer or, opposingly, how to make a firm mattress softer helpful if you think you have an issue with the comfort rather than the quality of the mattress itself.

Find the perfect memory foam mattress in our range

A memory foam mattress is one of the ultimate options for cushion and comfort in the bedroom, and they suit a wide range of sleepers, so purchasing one for yourself and letting it expand fully can lead to one of the dreamiest night's sleep you could imagine! Once it's all set up and ready, you can read our memory foam mattress cleaning guide to ensure you keep it in tip-top condition.

So, if this sounds like the kind of mattress you’d want to sleep on, why not check out our range of mattresses today? From single to king-size, use our Mattress Finder to discover the bed that will work best for you!

Don’t forget to visit our Snooze News sleep blog and Buying Guides as well for more tips and advice on how to get an even better night's sleep.