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How Long Does it Take a Memory Foam Mattress to Expand? | Sleep Blog

You just got your new memory foam mattress and took it out of the box. You cut the plastic and it begins to expand.

But then it stops. How long does it take a memory foam mattress to fully expand? What happens if it doesn’t expand all the way?

We will answer these questions and more in the sections below.


If your memory foam mattress is not fully expanded it will not provide the support and alignment needed for proper sleep. When fully expanded Memory foam mattresses are great mattresses, perfect for people that need extra back support or pressure relief.

Memory foam mattresses are great because they compress to fit your body. However, these mattresses usually come in small, compressed packages. As a result, you need to wait for them to expand before you can sleep on them. 

How Long Will It Take Your Memory Foam Mattress To Expand?

A memory foam mattress will usually take a minimum of 24 hours to finish fully expanding after being taken out of the packaging, but it can take up to 72 hours. However, it should grow to 90% of its size within four to six hours. 

Furthermore, mattress toppers take 24 hours to fully expand, whereas memory foam pillows take 48 to 72 hours. Pillows take longer to fill with air because they are denser. 

With that in mind, the time it takes for memory foam mattresses and products depends on several factors. Some of them have to do with how the manufacturer packages the product. However, some factors depend on what you do once you open the memory foam package. Finally, the environment can affect how fast your memory foam mattress expands.

Factors Affecting How Long It Takes Memory Foam Mattresses To Expand

Memory foam takes a long time to expand. The reason it takes so long to expand is the air gets squeezed out of the mattress when the manufacturer compresses it into packaging. 

Air needs to fill the open cell structure of the mattress once you remove it from the box. It takes time for the air to fill the space, so patience is a must. However, the time it takes for the mattress to expand can vary based on the product, manufacturer, and other factors.

Room Temperature

The first thing that can affect how long your memory foam mattress takes to expand is the bedroom temperature

Memory foam mattresses and other similar products will grow more quickly in warm environments. Heat reduces the viscosity of the memory foam and increases its fluidity. As a result, it becomes easier to mold, which in turn, allows air to get into the material faster. 

Foam Density

Another thing to consider is manufacturers do not make their memory foam products the same way. 

You would think the process would be similar because they are all called memory foam products. However, memory foam is more of a style than a precise recipe for a mattress. Some manufacturers produce denser memory foam than others, and density affects memory foam expansion.

Products made with denser memory foam will take longer to expand. Whether you purchase a memory foam mattress, pillow, or topper, it will take longer to inflate if it is denser. As a result, pillows take the longest to grow because of their dense structure. 

Memory foam is made denser for people who prefer firm mattresses and pillows. The denser the material, the firmer a sleeping surface you get.

Mattress Thickness

The final factor we want to look at is mattress thickness. If a memory foam product is thicker, it will take longer to expand. As a result, memory foam toppers will take less time to inflate than pillows or mattresses. There is no complicated answer for why thick mattresses take longer to expand. It takes longer because there is more space to expand into in thicker mattresses.

How To Speed up the Expansion Process

When your memory foam mattress arrives, you probably want to use it immediately. However, you must wait until it expands. Fortunately, there are some things you can do to speed up the expansion process.

Unbox Your Memory Foam Mattress Immediately

The best thing you can do if you do not want to wait to use your memory foam mattress is to avoid wasting time. Unbox it immediately and lay it flat on the floor. It is best to place it in your bedroom, so you do not need to worry about moving it once it is expanded. Laying it flat increases the surface area exposed to air, which will speed up the process.

Turn up the Heat

The next thing you can do is turn up the heat in your room. Ideally, you have a house where you can control the heat from room to room. If that is the case, you do not need to heat your whole home and increase your heat bill too much. Regardless, turning up the heat will reduce the time it takes to expand. 

Keep Good Air Circulation and Ventilation in the Room

The last thing you can do to speed up the expansion process is to ensure the room the mattress is in has fantastic air circulation and ventilation. If there is more air circulation, it is easier for air to get into the mattress and help it expand. 

Keeping it on a platformed bed works well because it is then easy for air to enter from the bottom. However, you can also use fan heaters to improve air circulation while increasing the temperature.

What Could Cause a Mattress to Not Fully Expand?

A few things could cause your memory foam mattress to not expand fully. The most common reason is leaving it in the box too long (sometimes this can happen if the manufacturer packed your specific mattress too early and left it in the warehouse for weeks before shipping it).

Most manufacturers recommend taking the mattress out of the box within 72 hours. Leaving it compressed for too long can negatively affect expansion.

It is also possible you need to be patient because the mattress is still expanding. While most beds fill with air within 24 hours, some can take up to 72 hours to expand completely. If the room is too cold or the product is denser, it will take longer to inflate than other products. 

Finally, it is possible to have a defective mattress. Unfortunately, you can get a defective memory foam mattress in the mail. It is common for cheap mattresses to fail to expand. If your bed does not inflate completely, it will be lumpy, unsupportive and have flat edges. If this is the case, take pictures for evidence and contact the manufacturer for a replacement.

How To Know if You Got a Faulty Memory Foam Mattress

It can be challenging to determine if your memory foam mattress is faulty out of the box. However, there are a few signs you can look for in your mattress. The most common issue is a mattress not fully expanding. 

If your mattress does not fully expand, it will have flat edges and lumps. Memory foam mattresses should be soft and pliable; if that is not the case, you probably have a faulty bed.

You can also tell if your mattress has issues after you sleep. Memory foam mattresses will usually have an indent longer than standard mattresses. However, it should bounce back quickly and not be too deep. If your memory foam mattress has an indent from your body deeper than a few inches, you likely have a faulty bed.

What Will Happen if You Do Not Wait 24 Hours for Your Memory Foam Mattress To Expand?

If you lack the patience to wait for your memory foam mattress to expand, you might wonder if something will happen if you forgo the 24-hour wait time. 

Fortunately, there are no significant issues with not waiting 24 hours for the mattress to expand. You cannot damage the memory foam by lying on it a little early. It can even be beneficial because your body heat will help the mattress expand more quickly. 

If you cannot wait 24 hours for your mattress to expand, it is recommended to wait at least 4 to 12 hours. In the first four to six hours, the off-gassing period takes place. 

During this time, the mattress lets off chemicals during early expansion. These chemicals are not toxic to most healthy people but can cause some discomfort to people with asthma or other breathing deficiencies. 

Finally, it is crucial to note that some manufacturers will tell customers it only takes eight hours for a mattress to expand fully. If that is the case, you should contact them to get all the details you must know about your purchase.

Final Thoughts

Memory foam mattresses are fantastic for people of all ages, especially if they experience neck and back issues. 

These mattresses support the human body better than most others and allow you to sleep comfortably. However, you must let the mattress expand after it arrives in a compressed package. Most should fully expand in 24 hours, but some factors can cause the timeline to increase to 72 hours.

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