What is a split king mattress, are they worth it and should you switch?

Image shows a Saatva Classic Split King Mattress on a beige fabric bedframe in a neutral colour bedroom
(Image credit: Saatva)

If you love sharing a bed with your partner but you hate their taste in mattresses, then it's time to consider buying a split king mattress. These clever 50/50 mattresses are split down the middle, so you can have a completely different feel, firmness and level of support and pressure relief to your partner's. In other words, you and your partner sleep on separate mattresses but on the same bed frame or base.

Split king mattresses are worth the money if you love a soft bed but your partner loves a hard bed and vice versa. They have plenty of benefits beyond customized feel too, including higher motion isolation. They are the ultimate solution if you and your partner have very different ideas about what is the best mattress for better sleep, meaning they could potentially end your sleep divorce.

They can be a lot more expensive than the best king size mattresses though, even in monthly mattress sales, so you need to know what you're getting for your money. Here we unpick everything you need to know about split king mattresses, who they do and don't suit, and the best one to buy right now.

What is a split king mattress?

A split king mattress pushes together two separate twin XL mattresses to form one big king-sized bed.While a normal king size mattress has the same firmness level throughout the bed, a split king size mattress can have different firmness levels on each side of the bed. However, a split king mattress can either be sold at the same or a higher price than a standard king.  

What is the size of a split king mattress?

A split king measures 76 inches wide by 80 inches long – the same dimensions as a standard king bed, meaning it's perfect for couples who enjoy a lot of space or are looking to expand their family. You can read our king size vs queen size mattress comparison guide if you’re unsure if a split king or king size may be too large for you.  

Are split king mattresses worth it? 

Yes — but it depends on how you sleep. If you’re a solo sleeper, a split king size bed is not worth it as these mattresses are not designed to accommodate those who sleep alone. Split king size beds are, however, designed for couples, so they’re definitely worth considering if you share a bed for a couple of reasons:

Two women laugh and talk while lying on a split king mattress

(Image credit: Getty Images)

They're great for couples with different sleep styles and body weights

If you’re petite and like to sleep on your side, but your partner has a heavy build and likes to sleep on their stomach (or vice versa), you’re going to prefer different mattresses. Some sleepers, such as lightweight side sleepers, need something soft and plush, while a heavyweight stomach sleeper will need a firm bed. 

Although a medium-firm mattress can be a good middle ground (and suit back sleepers), a split king can have one plush mattress and one firm mattress pushed together so no one has to compromise.

They stop your partner’s constant in-bed wriggling waking you up

If your partner has a tendency to toss and turn at night or you both operate on different sleep schedules, this can sometimes mean that you can feel the movement of your partner wriggling or getting out of bed on the other side of the mattress. 

While some mattresses use special materials, such as memory from or individually wrapped springs, to provide motion isolation (the prevention of motion transferring across the bed), they aren’t always effective. With a Split King, you and your partner sleep on separate mattresses, so you won’t be disturbed by your partner’s movements.

Can you feel the crack in a split king mattress?

If you’re concerned that the gap between the two mattresses will feel uncomfortable or slide apart when sleeping closely to your partner, there's no need to worry. There’s no danger of the mattresses separating, and as for comfort, most sleepers can’t even feel the gap. 

However, it’s not impossible to feel the gap, and some mattress brands suggest getting a topper to cover it up — but this method goes against what the split king is designed for: providing separate sleep surfaces.

A person holds their hand on the Layla Essential Mattress cover

(Image credit: Future)

If you’re concerned about the gap, it may be worth trying out a split king in-store or at a mattress viewing room. Not trying out a mattress is one of the big mistakes couples make when buying a first mattress, so look for brands that offer an at-home sleep trial, enabling you to literally sleep on your decision. Most mattress brands include a sleep trial of up to 100 nights, but DreamCloud and Saatva are among the many mattress companies offering a year's free trial. 

Can you use a split king mattress with adjustable beds?

Yes, split king mattresses are perfect for using with adjustable beds as not only will you reap the benefits of superb motion isolation, you'll be able to tailor your mattress better when it's placed on an adjustable bed. For example, if you need to sleep on your side and at an incline to reduce snoring, but your partner likes to lie flat on their back to sleep, you can each position your side of the split king mattress accordingly with an adjustable bed base. 

Adjustable beds can be raised or lowered via app, remote control or integrated buttons on the bed itself. The smartest options, such as the Tempur-Pedic Tempur Ergo Base, can also detect snoring, monitor your breathing and heart rate during sleep, and cradle your body in a zero gravity position to reduce pain and pressure points.

What is the best split king mattress to buy?

While some brands, such as Casper and Helix, don’t sell split king versions of their mattresses, a lot of mattress brands do. While those who do make split kings tend to split standard king size mattresses, some (such as Saatva) carry a split California king size, too. 

However, it’s important to remember that some mattresses with a split king option don’t have adjustable firmness, meaning you won’t be able to tailor the softness to fit your build. Here is our top picks for a split king mattress with adjustable firmness.

Saatva Classic Hybrid: $2,790 $2,440 for a split king at Saatva

Saatva Classic Hybrid: from $2,790 $2,440 for a split king at Saatva
The Saatva Classic is the best hybrid mattress in the world. Not only does this fiberglass-free luxury hybrid come in both a split king and a split Cal king, it also has three firmness options. While a lot of brands charge extra the plusher you go, all firmness levels are priced the same. In addition to its customising options, its cooling properties and excellent pressure relief were praised in our Saatva Classic mattress review. If possible, you and your partner can also go to one of Saatva’s viewing rooms to try out their split king to see if it feels right. Right now you can save $400 off a split king Saatva Classic, reducing the price to $2,390 (was $2,790). The Saatva Classic also comes with a 365-night trial, lifetime warranty and free white glove delivery with old bed removal.

Should you switch to a split king mattress?

If your idea of a comfy mattress is wildly different to your partner's, yet you want to share a bed with them, then yes we definitely recommend switching to a split king mattress. Doing so means you will each have the perfect mattress feel, firmness, support and pressure relief for each of your bodies, while still sharing the same bed frame. So your side of the bed will feel very different to your partner's. 

Split king mattresses are more expensive than standard king size beds, but the benefits are far better. Make sure you shop around for the best price on the split king mattress you're buying, and consider adjustable bed and mattress combos too as these will save you more money than if you were to buy both items separately. 

Frances Daniels
Sleep Staff Writer

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