How long does it take a memory foam mattress or topper to expand?

It may take 24–72 hours for a memory foam mattress or topper to fully expand. It expands up to 90% in about 4-6 hours and requires a few more hours to completely expand. Therefore, it is advised to wait 24 hours before sleeping on a memory foam mattress topper. 

However, sometimes it may take more days to fully expand. Please don’t worry if you find the mattress or topper you received did not expand so quickly. There are 3 possible reasons that prolong the expansion process:

• You have a very low room temperature
• The mattress or topper is high density and thickness
• The mattress or topper stays wrapped and rolled inside the shipping box for a pretty long period 

Memory foam is temperature-sensitive. Heat improves the viscosity of the foam and increases its pliability, making it easier to mould. It feels firmer in a cooler environment. it will expand much faster as the temperature goes up.

The expansion time of memory foam depends on how thick and dense it is. Generally, the denser the mattress or topper is, the firmer it is, and the longer it takes to fully expand.

A memory foam mattress or topper is deflated, folded, and packed in a box. If the mattress or topper stays too long in the package it takes more time to expand. So, when receiving the package, it’s better to unpack it immediately. 

Here are several tips to speed up the expansion process:

1: Put the Mattress On the Floor and Wait 72 Hours

Time is often the most effective solution here. Most modern memory foam mattresses are designed to expand fully in just a few hours so that you can sleep on them the same night. However, you’ll find that many brands will say that it can take up to 72 hours for complete expansion. Now, if you’ve already tried this then you might have some better luck if you move the mattress onto a hard surface like the floor because this can encourage expansion.

If you’ve yet to wait 72 hours and you have nowhere else to sleep, then you should be fine sleeping on it on the first night (as long as this doesn’t void the warranty/return policy) – this can actually help expansion in many cases as described in step 4.

2: Warm the Room Up to at Least 20°C (68°F)

Memory foam is temperature-sensitive. Cold inhibits expansion whilst warmth encourages it. So if your room is cold, then you should heat it up until you’ve hit the average room temperature of 20°C (68 °F) – or slightly more. If the mattress still hasn’t expanded fully after 72 hours using the temperature and floor technique then move on to step 3.

3: Roll On the Mattress For 10 – 30 Minutes

In addition to heat, movement can help to loosen memory foam up which can encourage inflation. If you roll around on the mattress for between 10 and 30 minutes you may find that the memory foam starts to soften – allowing the mattress to expand fully. You may find it more effective to just switch between various sleeping positions – holding each position for 5 – 10 minutes to allow the foam enough time to become warm and adjust to your body shape. This technique alone can help fix your memory foam mattress if the middle or corners are deflated. But I advise against standing on the bed because this type of concentrated pressure may negatively affect the memory foam – possibly leading to indentations or damage to the support core.

4: Sleep on the Mattress for a Week

If you’ve seen some minor improvement (or even none at all) after step 3, then sleeping on the mattress for a few days or a week might do the trick. Because by spending a full night on the mattress, you’re allowing it to adjust to your body heat and weight for a prolonged period which may encourage full expansion. It can take memory foam mattresses up to a month or more under normal conditions to begin to feel comfortable as it conforms to your sleeping style. At this point, you may no longer care that your mattress isn’t fully expanded, and you are comfortable sleeping on it.