What is the biggest mattress size and where can you buy it online?

The Nolah Luxe Alaskan King Mattress in a large bedroom, with four pillows showing just how bug the mattress is
(Image credit: Nolah Mattress)

The biggest mattress size can make the perfect bed for large families, couples, and co-sleepers. An oversized mattress is also great for taller individuals or restless sleepers who want more room to wriggle and stretch out. But what is the biggest mattress size and where can you buy it online?

While most of the beds we test for this year's best mattress guide have king or California king as their biggest mattress size, there are actually larger beds than king and Cal king on the market. These oversized mattress sizes are much rarer, however, so they are harder to shop for online. 

Here, we'll explore some of the biggest mattress sizes on the market, their measurements, and which one to choose to benefit your sleep. As their less accessible than standard mattress sizes, we'll also go over where you can buy one online in the mattress sales

What is an oversized mattress?

In so many words, an oversized mattress is any mattress that's larger than a king (80" x 76") or California King (72" x 84") mattress. Most mattresses usually come in twin to Cal king, with some brands offering more unusual sizes (such as RV king or short queen).

A chart of mattress sizes from King to Alaska King

(Image credit: Getty Images)

While a king mattress tends to be large enough for most people, there are some advantages to going bigger and buying an oversized mattress. For example, parents who co-sleep with their young children or pets may want to have a larger bed for sharing, while some parents may want a larger bed where friends and family can relax and talk together for sleepovers, movie nights, or simply spending time together. 

However, these oversized beds are not for those on a tight budget, nor are they for those whole live in small houses or apartments. Purchasing an oversized mattress alone (without a foundation) can set you back around $3,500.

What is the biggest mattress size?

a cartoon of a young family co-sleeping

(Image credit: Getty Images)

Measuring at a whopping 144” x 84”, a Family XL King is the biggest mattress size. This is a specialist bed suited for multiple people (around 6) and gets its name from its ability to accommodate co-sleeping families. 

You can also get the slight smaller Family King, which measures at 120” x 80”. Again this is suitable for co-sleeping families. 

Oversized mattress size guide

Swipe to scroll horizontally
Family XL 84" x 140"
Family 80” x 120"
Alaskan king108" x 108"
Alberta king96" x 96"
Wyoming king84" x 84"
Texas king80" x 98"

How to choose an oversized bed

When choosing a mattress that's right for you, size matters. To pick the right oversized mattress size, you need to consider a number of things, from the size of the room to the size of the sleepers. 

Here are some things to consider when choosing an oversized mattress.

1. Number of sleepers

A St Bernard dog shares a bed with two young children

(Image credit: Getty Images)

Many families with young children co-sleep, meaning they'll need a wider sleep space to accommodate multiple sleepers, so you need to decide how much room your family needs if you share one bed. 

A lot of people have their four-legged friends sleep in their bed, too. If you have a lot of pets sharing your bed or your pets are quite large, you may want to consider how much room you'll all need,

2. Room size

A woman stands by a window of a sunlit bedroom in the summer

(Image credit: Getty Images)

A big mattress requires a big room, not to mention a big house to allow enough space for delivery and set-up. Oversized mattresses are designed for those with big houses and bedrooms, so make sure that you take measurements and properly gauge whether the bigger mattress sizes will actually fit. 

3. Body size

A chart looking at the dimensions of a Wyoming king bed

(Image credit: Getty Images)

While most couples can manage with a king, Cal king, queen, or even a full, couples with varying body weights and heights may need something bigger. That means you should consider whether you need a wider bed or a longer bed. For example, a tall individual or couple will need something bigger in length, so should go for an Alberta or Wyoming king rather than a relatively short Texas or Family king. 

4. Cost and extras

Oversized mattresses are for those with a big budgets, usually costing over $3000 - and that's just for the mattress. You'll also have to pay a hefty price for a foundation and find suitable bedding to fit such a large bed, which can be tricky to look for. 

Where can you buy an oversized mattress?

The Nolah Luxe Alaskan King Mattress against a white background, with a cut out showing the interior of the mattress

(Image credit: Nolah Mattress)

While the most popular, well-known mattress brands don't carry sizes larger than Cal king or king, that doesn't mean it's a herculean feat to find one. For example, there are many sites that specialize in make custom-built oversized mattresses. 

There are also some famous brands that do carry a size larger than Cal king. For instance, Nolah recently introduced an Alaska King mattress to their line-up. In fact, you can currently save $2,750 on Luxe Alaskan King Mattress at Nolah Sleep thanks to its 35% off sale. 

Frances Daniels
Sleep Staff Writer

Frances Daniels is a Sleep Staff Writer at Tom's Guide and her role includes covering all mattress and sleep news, in addition to mattress reviews and buyer's guides, plus sleep accessories such as pillows and mattress toppers. Frances is a PPA-accredited journalist and is hugely interested in the relationship between good sleep and overall health. When not writing about mattresses and sleep for Tom's Guide, Frances enjoys writing about women's issues, health and wellbeing, the environment, and her native Wales.