I'm a mattress expert — the No 1 mistake people make after buying a bed in a box

Two people removing a Purple mattress from its packaging

(Image credit: Purple)

Boxed mattresses have revolutionised how well we sleep, giving us the same quality of traditional, often more expensive mattresses at a fraction of the price. Part of my job involves testing beds-in-a-box for support and comfort, so I’m well-versed in how to handle this type of mattress.

While they are very easy to set up, there is one giant mistake that I see people making on a regular basis – and it costs them dearly. Here I’ll talk you through what to avoid once your new bed arrives and what to do instead.

Many of 2024’s best mattresses for all sleepers and budgets come in a box, so you’ll have plenty of choice available if you do decide to upgrade soon.

The No 1 mistake people make after buying a boxed bed

Boxed beds are mattresses that have been compressed by a heavy weight, rolled in protective plastic, then shipped in a box to your front door.

I’ve tested many of this year’s best mattresses in a box and all of them come with a simple rule. Unfortunately it’s one that a lot of people choose to ignore.

After choosing a mattress and getting it shipped home, the biggest mistake people make when buying a boxed bed is not opening it soon after receiving it. By being left tightly compressed and rolled in a shipping box for several months on end, these mattresses are at risk of damage to the materials, shape and performance.

Image shows the Emma Original mattress tightly rolled and covered in tough plastic — (Image credit: Future)

Mattress manufacturers then deem these beds unfit for purpose. Chances are that when you finally get around to unboxing it and placing it on your bed, it will stink heavily of off-gassing, may have bulging coils if it’s a hybrid mattress, or be misshapen with an uneven sleep surface. Some memory foam beds left for too long in their box may not contour your body properly.

You will have little chance of returning a boxed mattress for a refund or exchange if you haven’t removed it from packaging within the timeframe set out by the manufacturer, so you’re then stuck with a defective mattress that isn’t suitable for sleeping on and that cannot be returned.

How long can a mattress in a box stay in the box?

Mattress manufacturers each have different unboxing and setup guidelines as we’ll explore below, but most urge you to unbox your mattress and remove its packaging as soon as you take delivery of it.

This helps the roll-up mattress to expand fully and to achieve its best shape for supporting your body over the years to come. Here’s how long some of the best hybrid mattress and memory foam mattress brands say you can leave the mattress in its box for:

Zinus Mattress – No longer than a week
Purple Mattress – Within two weeks of delivery
EmmaMattress – No longer than four weeks of delivery
Tuft & Needle – Within three to four weeks of delivery
Nectar Mattress – Within 90 days of delivery
DreamCloud Mattress – Within 90 days of delivery
Casper Mattress – Up to three months after delivery

The other issue with leaving your mattress in its box for too long is you’re sacrificing a lot of your sleep trial. I recommend sleeping on a new bed for at least 30 consecutive nights to make sure it definitely suits your body and sleeping position.

With the average mattress trial lasting for 100 nights, you won’t leave yourself much time to make sure you’ve chosen the right bed if you leave the mattress boxed for weeks first.

Siena Sleep memory foam mattress, featuring a person lying upside on the bed, with legs up the wall, reading a book — (Image credit: Siena Sleep)

What do when you receive a mattress in a box

I receive a lot of boxed mattresses for testing each year and I never leave them sitting around in their packaging for long. Here’s what I’d recommend you do once you receive your new mattress, to avoid making common mattress unboxing mistakes:

Check the shipping docket to make sure it’s the right mattress in the right size.
Check the shipping docket or order to see if there’s any confirmation of the date the mattress was compressed and boxed for shipping.
Open the box, remove the mattress and place it on your bed frame.
Use the included plastic cutting tool (if provided) and open the reinforced plastic covering.
Strip all packaging from the mattress then place the mattress on your bed and leave it to expand.
Follow the manufacturer’s guidelines on how long to let it expand for before sleeping on it.
Open a window to allow any off-gassing smell to dissipate.

Claire is a fully qualified journalist and Certified Sleep Science Coach with over 15 years’ product review experience. Claire is responsible for all mattress and sleep content published on Tom’s Guide, including our Best Mattress of 2025 buying guide. She is our expert on Saatva, DreamCloud, Nectar and Tempur-Pedic mattresses, and is also our in-house hybrid mattress specialist. Claire is certified to advise people on how to choose a mattress that best suits their sleep, body and budget, as well as helping them to create a nighttime routine and bedroom environment that promote good sleep. As Senior Sleep Editor, Claire takes the lead on developing and overseeing rigorous testing procedures for our mattress reviews, both at home and in our fully equipped Sleep Studio. Claire leads a team of experienced sleep and mattress specialists who report on and test a wide range of mattress and sleep products, and she also writes about all things related to sleep, and has interviewed a wealth of experts including mattress designers and buyers, neuroscientists, and doctors of sleep medicine.