A split king is two Twin XL mattresses sized to match a standard king. Here is how it works with adjustable bases, which sheets fit, and how to stop the halves from drifting apart.
Split king is one of the few mattress terms that is genuinely confusing, because it is not a mattress size in the way queen or king is. It is a configuration. Understanding that one distinction answers most of the questions people have about it: what it measures, why sheets are a problem, why it exists at all, and whether it is right for your bedroom. Here is the full picture.
A split king is two Twin XL mattresses placed side by side. Each Twin XL measures 38 inches wide by 80 inches long, so together they cover 76 by 80 inches, which is exactly the footprint of a standard one-piece king mattress. Your bed is the same size on the floor. The difference is that it is two independent pieces rather than one.
That independence is the entire point. A single king mattress cannot bend in two places at once, so it cannot sit on a dual adjustable base. Two Twin XL mattresses can, and each side articulates on its own.
Three similar-sounding configurations get mixed up constantly.
If your main reason for going split is that one of you wants the head raised at night, a flex head king is worth asking about before you commit to a full split. For more on how the sizes compare on paper, see our guide to king vs California king and our Twin XL size guide.
This is the number one reason. One partner raises the head to read, watch something, ease acid reflux or reduce snoring, while the other stays flat. On a one-piece king, that is simply not possible. Browse our adjustable bed collection to see how dual bases work, and read up on the zero gravity position.
Underrated and often the more important benefit. Because the halves are separate mattresses, they do not have to match. A side sleeper who needs a plush surface and a stomach sleeper who needs firm support can finally stop compromising on a medium that suits neither of them. They can be different firmnesses, different constructions, even different brands.
Two physically unconnected mattresses cannot transmit movement to each other. If one of you gets up at 5am, the other side does not move at all. No single mattress, however good its foam, matches that.
Two Twin XL mattresses are far easier to carry up a staircase or around a tight LA apartment corner than one king. Anyone who has tried to bend a king mattress through a doorway will appreciate this.
A split king is not the right answer for everyone, and it is worth being honest about why.
This trips up almost everyone. A standard king fitted sheet will not work, because it would tie the two halves together and stop the base from articulating.
What you need instead:
For the top layers, a king or California king comforter, duvet and flat sheet lie over both halves normally. They just move with the bed rather than being tucked in tightly. For a split California king you need split California king fitted sheets specifically, which are much harder to find. Our guide to keeping sheets on an adjustable bed covers the fit problem in more detail.
Drift is the most common complaint, and it is solvable. In rough order of effectiveness:
Hard floors and slippery base fabrics make drift worse. If the bed is on tile or hardwood, dealing with the frame first usually solves it permanently.
Not every mattress works on an adjustable base. You need one that flexes without damage, which in practice means foam, latex or a hybrid with pocketed coils. A traditional connected-coil innerspring will not bend repeatedly without breaking down. Check the manufacturer's guidance before you buy, and read our guide to choosing a mattress for an adjustable bed. If a full split king is more bed than you need, a split queen gives you the same independence in a smaller footprint.
A split king needs the same floor space as a king, so plan on a bedroom of at least 12 by 12 feet, and 12 by 14 or larger if you want nightstands on both sides. That matters here, where a lot of the housing stock is older and bedrooms run small. Our guide to average bedroom size and what actually fits has the clearance math. The upside for LA apartments is real, though: two Twin XL mattresses and a two-piece base will get through a stairwell that a one-piece king simply will not.
It is two Twin XL mattresses, each 38 by 80 inches, placed side by side to cover the same 76 by 80 inch area as a standard king. Because the halves are separate, each one can sit on its own adjustable base and move independently.
It is two Twin XL beds, which is not quite the same thing. A regular twin is 38 by 75 inches, five inches shorter than a Twin XL. Two regular twins side by side come to 76 by 75 inches, which is shorter than a king and will leave your sheets and frame mismatched. Twin XL is the correct half.
76 inches wide by 80 inches long in total, made of two 38 by 80 inch Twin XL halves. It is the same overall size as a standard king mattress.
Yes, in footprint. Both measure 76 by 80 inches. The difference is construction, not dimensions: a king is one piece, a split king is two.
A split king sheet set usually includes two Twin XL fitted sheets, one king flat sheet and two king pillowcases. The fitted sheets have to be separate so each half of the bed can move independently; a single king fitted sheet would hold them together and defeat the purpose.
Install the retainer bars that came with your adjustable base, connect the two bases with the manufacturer's bracket or strap kit, and add a mattress connector strap or a foam gap filler across the seam. Non-slip pads under each mattress help on slick surfaces.
Two halves measuring 36 by 84 inches each, totaling 72 by 84 inches. It is narrower per side than a split king but four inches longer, which suits taller sleepers. The halves are a non-standard size, so mattresses and fitted sheets are harder to find and cost more.
Each half is 38 inches wide, the width of a Twin XL. A one-piece king is 76 inches across, so each sleeper gets the same 38 inches either way. You give up no personal width by going split, only the continuous surface in the middle.
A split king is easier to understand lying on it than reading about it. All five of our Los Angeles showrooms have dual adjustable bases set up so you and your partner can raise each side independently, feel how noticeable the center seam is, and try two different firmness levels side by side before deciding. Browse adjustable beds and Twin XL mattresses to start, take our sleep quiz for a firmness recommendation for each of you, or read our adjustable bed FAQ. Same-day delivery is available across Los Angeles, and every mattress comes with our 120-night comfort guarantee, so if one side turns out to be the wrong firmness you can change just that half.
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