In one sentence
A split king is two 38 x 80-inch Twin XL mattresses, so the whole bed is 76 x 80 inches, the same as a King. Most people use one King comforter. If you prefer not to share bedding, use two smaller comforters; by our size chart math, Twin XL is the closest fit per side.
Split King, Split California King and FlexTop King
| Measurement | Split King | Split California King | FlexTop King |
|---|---|---|---|
| How the bed splits | Two mattresses, split down the entire bed (Sleep Number) | Two mattresses, 36 x 84 in each (Sleep Junkie) | Splits only at the head (Sleep Number) |
| Total sleeping surface | 76 x 80 in, same as King | 72 x 84 in, same as California King | 76 x 80 in |
| Comforter size to start with | King: 102–110 in wide (our size chart) | California King: 104–114 in wide (our size chart) | King: 102–110 in wide (our size chart) |
| Calculated side drop, centered flat | (102–76)/2 to (110–76)/2 = 13–17 in | (104–72)/2 to (114–72)/2 = 16–21 in | (102–76)/2 to (110–76)/2 = 13–17 in |
| Fitted sheets (Sleep Number) | Two, 38 x 80 in each (Twin XL) | Two, 36 x 84 in each | One, 76 x 80 in |
| Flat sheet (Sleep Number) | One, 110 x 100 in | One, 106 x 104 in | One, 110 x 100 in |
When two comforters make sense
You prefer not to share bedding
Sleep Foundation names this as the reason to use smaller bedding separately on a split king. Each person gets their own comforter, and each can pick a different weight.
You raise your sides at different times
On a split adjustable base, each half can rise on its own. Two comforters let each person manage their own cover. That is our reasoning from how the bed is built, not a test result.
What is a split king bed?
A split king is two mattresses placed side by side. Each one is a Twin XL, which is 38 inches wide and 80 inches long. Together they measure 76 x 80 inches. Sleep Foundation and Sleep Junkie both say that is the same size as a standard King.
Tempur-Pedic describes a Split King as equal to two Twin XL products. Many split kings sit on a split adjustable base. Then each side of the bed can be raised on its own, so one person can sit up while the other lies flat.
Split king bedding usually means a sheet set with two Twin XL fitted sheets and one King top sheet, according to Sleep Foundation. The bottom layer is split. The top layers are King size.
What size comforter fits a split king?
A King comforter. It lies on top of both mattresses, so it only has to cover the 76 x 80-inch surface. Sleep Foundation says you can buy King-size options for the rest of the bedding, because a split king is the same size as a standard King.
Our comforter size chart lists King comforters at about 102–110 inches wide by 86–100 inches long. Side drop is how far the comforter hangs over each side. For a centered comforter lying flat, use (comforter width − mattress width) / 2.
A 102-inch King gives (102 − 76) / 2 = 13 inches per side. A 110-inch King gives (110 − 76) / 2 = 17 inches per side. These are flat-bed numbers, not a promise of coverage. A deep mattress leaves less fabric below the edge.
If 13–17 inches is not enough for your bed, our oversized King guide compares wider options.
One King comforter or two separate comforters?
Most people make a split king the same way as a standard King, with one King comforter or quilt on top, says Sleep Foundation. Sleep Junkie also lists a King comforter or duvet across the top. If you share bedding on a King now, nothing changes.
Two comforters are the other option. Sleep Foundation says that if you prefer not to share bedding with your partner, you can use smaller bedding separately. With two comforters, each person can also choose their own warmth.
An adjustable base adds one more thing to think about. Each half can rise on its own. One comforter lies across both halves, so it spans the seam when one side is up and the other is flat. Two comforters keep each person's cover separate. This is reasoning from how the bed is built, not a test.
What size should two separate comforters be?
The sources do not name one size for separate comforters. Sleep Foundation only says smaller bedding. We start with Twin XL, because each half is a Twin XL mattress. That is our choice, based on our own size chart.
Our size chart lists Twin XL comforters at about 66–68 inches wide by 90–92 inches long. One half of a split king is 38 inches wide. So a Twin XL comforter is 28–30 inches wider than its half. Centered on that half, it hangs 14–15 inches over each side.
That includes the middle. Each comforter reaches 14–15 inches onto the other person's half, so the two comforters overlap. Side by side, they add up to 132–136 inches of width on a 76-inch bed.
For length, 90–92 inches on an 80-inch mattress leaves 10–12 inches extra. That has to cover the foot drop and the space near the pillows. Check the exact listing, because sizes vary by brand.
What about a split California King or FlexTop King?
A split California King uses two 36 x 84-inch halves. Together they make 72 x 84 inches, the size of a California King, says Sleep Junkie. It also notes that split California Kings are less common.
Start with a California King comforter. Our size chart lists them at about 104–114 inches wide by 96–104 inches long. On a 72-inch bed, that gives (104 − 72) / 2 = 16 to (114 − 72) / 2 = 21 inches per side when centered flat.
A FlexTop King is different. Sleep Number says its FlexTop King splits only at the head, so each side can raise the head of the bed on its own. Its Split King splits down the entire bed. The FlexTop King uses one 76 x 80-inch fitted sheet, so the comforter choice is the same as for a King.
What still needs to be split?
The fitted sheets. Sleep Foundation says the fitted sheets let each mattress move on its own, while the top sheet can be shared. Sleep Number's Split King and Split California King sets also contain two fitted sheets.
Sleep Junkie adds that one King fitted sheet works only if the bed stays flat. On a split adjustable base, each half needs its own Twin XL fitted sheet. The comforter and flat sheet can stay King size.
How do you measure for a split king comforter?
Measure the full width across both mattresses. A standard split king should be about 76 inches wide. Measure the length and the mattress depth, too.
Decide how far you want the comforter to hang on each side. Then use this rule: target width = mattress width + 2 × desired side drop. For a 15-inch drop on a 76-inch split king, that is 76 + 30 = 106 inches.
Our size-drop calculator does the math with your own numbers. Compare the result with the actual width and length on the listing, not just the size name.
Frequently asked questions
What size comforter do you need for a split king?
A King comforter. A split king measures 76 x 80 inches in total, the same as a standard King. A King comforter 102–110 inches wide gives about 13–17 inches of drop per side when centered flat.
Source: Sleep Foundation: What is a split king bed?, Sleep Junkie: What is a split king?
Can you use a king comforter on a split king adjustable bed?
Yes. Sleep Foundation says most people use a King comforter or quilt on a split king, and Sleep Junkie lists a King comforter or duvet across the top. The comforter spans both halves. If you prefer not to share, two smaller comforters are an option.
Source: Sleep Foundation: What is a split king bed?, Sleep Junkie: What is a split king?
What is a split king bed?
Two Twin XL mattresses, each 38 x 80 inches, placed side by side. Together they cover 76 x 80 inches, like a standard King. On a split adjustable base, each side can be raised on its own.
Source: Sleep Foundation: What is a split king bed?, Tempur-Pedic split mattress ordering help, Sleep Junkie: What is a split king?
What is split king bedding?
Usually a sheet set with two Twin XL fitted sheets and one King top sheet. The comforter can be King size, because the bed has the same footprint as a King.
Source: Sleep Foundation: What is a split king bed?, Sleep Number Essential Fit sheet sizes
Can you use two Twin XL comforters on a split king?
Yes, if you prefer not to share bedding. Sleep Foundation says smaller bedding can be used separately. By our size chart, a 66–68-inch Twin XL comforter hangs 14–15 inches past each side of a 38-inch half, so two of them overlap in the middle.
What size comforter fits a split California King?
A California King. A split California King is two 36 x 84-inch halves, or 72 x 84 inches in total. Our size chart lists California King comforters at about 104–114 inches wide.
Source: Sleep Number Essential Fit sheet sizes, Sleep Junkie: What is a split king?
Sources and editorial method
We checked definitions and practical distinctions against the sources below. Product recommendations live in separate buying guides with their own criteria and disclosures.
The bottom line
A split king is a King-size bed in two parts. Use a King comforter unless you want separate bedding. If you do, two Twin XL comforters are our size-chart starting point, and they overlap in the middle. Only the fitted sheets must be split.