If you’ve ever bought a new mattress, you know the excitement you feel when it’s finally there and ready for you to sleep in. At last, you get to put on your clean sheets, arrange the pillows to perfection, and dive right in.

With most mattresses, you don’t really have to wait to lie down and bask in the feeling of your new paradise. However, if you opt for a memory foam model, things are a bit different. Namely, they take some time to expand and be ready for use, meaning that you can’t just use them as soon as you buy them.

But how long does a memory foam mattress actually take to expand? Can you sleep on it before it’s fully ready? And can you help speed up the expansion process somehow? Stay tuned to find out in our complete memory foam mattress guide.

What Are Memory Foam Mattresses?

A memory foam mattress is also known as a bed in a box, which is a name that can tell you a lot about its definition. Put simply, these types of mattresses are first compressed, then packed into neat boxes that can be easily shipped to your home.

Amazingly, the compression takes nothing away from the quality of the memory foam. It is a highly flexible material, and its main characteristic is that it can deflate and expand however many times necessary.

Thus, when you open the box and take the mattress out, it starts slowly expanding. The foam begins changing and growing right before your eyes, and the mattress soon starts taking shape.

Memory foam mattresses are quite popular precisely because of their ability to change shape. When you lay down on a mattress like this, the cells slowly mold to the shape of your body.

Thus, the mattress supports your limbs and torso perfectly, allowing each part of your body to get the rest it needs. Even better, the cells slowly pop back into place when you get up. So, the mattress ends up brand new once again when you get into bed later on.

Most people who buy memory foam mattresses want to improve their quality of sleep. Some also need more support for their back or legs, and memory foam is the perfect solution. However, sleeping on these mattresses is advisable for everyone, even if they are completely healthy.

How Long Does the Expansion Take?

Most memory foam mattresses take between 6 and 10 hours to expand completely. However, all manufacturers advise that waiting at least 24 hours before using your foam mattress is the best option.

During these 24 hours, the memory foam has more than enough time to expand entirely, allowing your mattress to reach its full potential. The mattress itself will be firm and comfortable, and you’ll be able to enjoy all its benefits.

Safety-wise, it is also smart to wait out the proposed stretch of time. Only when the foam expands fully can you see if there are any cracks or splits in the material. Thus, giving the foam some time is imperative to make sure that you get a flawless product for the money you have spent.

Certain companies advise that you wait even longer, up to 48 hours after taking the mattress out of its case. In most cases, these manufacturers simply choose to err on the side of caution. As long as you wait 24 hours, your mattress should be more than ready.

What Factors Determine How Fast a Memory Foam Mattress Will Expand?

There are 3 factors that can affect a memory foam mattress’ speed of expansion. These factors are valid for every product, no matter which manufacturer made it.


Generally speaking, memory foam cells are extremely temperature-sensitive. In other words, they shrink in colder environments and expand in warmer ones, just like the cells in our bodies.

So, anything made from memory foam will have a harder time expanding in cold rooms. With that said, expanding will not be impossible. It will simply take a bit more time. Conversely, warmer environments can have the opposite effect.


When shopping for memory foam mattresses or pillows, you can usually choose between models of different firmness. Your decision should depend on your overall preferences or any advice you got from your doctor.

However, it is important to mention that this decision also affects how fast the product will expand. Namely, the firmer the mattress, the denser the memory cells.

When a mattress is made of denser layers of cells, it usually takes some extra time to expand. It is easy to see why, as a larger number of cells logically require more time to grow and reach the intended shape.

So, if you need a mattress that will expand as soon as possible, try going for less dense models. Still, waiting a bit longer might be worth it, as firmer mattresses usually have a longer shelf life.


If you compare pillows and memory foam mattress toppers, you will notice that there is a significant discrepancy between how fast they can expand. Namely, pillows often take a few hours more than toppers, simply because they are thicker.

Thus, your mattress will behave similarly. The thicker it is, the more time it will need to expand fully. For example, a mattress that is 2 inches thick will expand in about 6 hours. On the other hand, a model that is 4 inches thick might need 4 hours more.

It is important to note that thicker mattresses do not automatically contain more memory foam cells. In other words, density does not equal thickness. Thus, be careful as you shop and consider these two factors separately.

Is There Anything You Can Do to Make Your Mattress Expand Faster?

As mentioned above, memory foam cells are sensitive to temperature changes. Luckily, this characteristic gives you an opportunity to speed up the expansion process of your mattress.

Therefore, if you want your mattress to be ready sooner, you can try adjusting your thermostat. Make sure your room is a few degrees warmer than usual, and watch as the magic unfolds.

Besides using this trick, you can also warm up your mattress the old-fashioned way. Simply lay on it, and let your body heat transfer onto the expanding cells.

What Happens If You Don’t Wait for the Expansion to Be Done?

If waiting 24 hours is simply unacceptable for you, worry not. In general, you can try out your mattress as soon as it has taken its shape and is firm to the touch. Most importantly, lying down on it won’t halt or disrupt the expansion process in any way.

In other words, your mattress will be completely fine even if you use it before the 24 hours are up. What’s more, your body heat might even help speed up the process, which is a win-win.

With that said, don’t use the mattress right after taking it out of its box. Give it at least an hour or two. Otherwise, it won’t be soft at all, so you won’t be able to be comfortable and actually get rest.

What If the Memory Foam Doesn’t Expand?

As mentioned above, your mattress will need at least a few hours to start taking shape. Only then will it gain its usual softness and firmness. So, don’t be concerned if what you can see in the first hour or two doesn’t really resemble a cozy sanctuary you’d love to dive into.

However, if your mattress is still lumpy and lifeless after a few hours go by, you definitely have a problem. No matter how big the mattress is, it has to start expanding and taking shape within a 2-hour period.

If you think there might be something wrong with the mattress, you should call the manufacturer or the store you bought it from immediately. That goes both for small defects in the foam and for mattresses that don’t expand at all.

In most cases, such situations occur because the memory foam is faulty. It could be filled with air, or there might be cracks between memory cells. The cracks could be preventing the mattress from taking its intended shape.

Whatever the issue might be, you should contact the mattress’ parent company. After you have explained the problem to them, you will most likely receive a new mattress in a few days’ time, and the problem will be behind you.

To Sum Up

Memory foam mattresses are quite handy. Besides their ability to fit in small boxes, they are also incredible for your back and can help you sleep better. However, the very thing that makes them so beneficial also prevents you from using them as soon as they arrive. Namely, the memory cells inside the mattress take a certain amount of time to expand fully.

To be able to use the mattress and enjoy its full potential, you will have to wait somewhere between 6 and 10 hours. If you want to be extra cautious, giving the mattress a full day is the safest option. That way, you’ll be sure that there are no defects and that the mattress is truly ready for you.

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