What Size Is a Split King Mattress? Dimensions, Fit, and FAQs

If you’re wondering “What Size Is a Split King Mattress”, you’re likely trying to figure out how it compares to a standard king, what sheets it needs, and whether it will fit your bedroom. This guide breaks down the exact dimensions and answers the most common questions about split king mattresses.

What Size Is a Split King Mattress?

A split king mattress is made of two separate twin XL mattresses placed side by side.

  • Each twin XL mattress: 38" wide x 80" long (approximately 96.5 cm x 203 cm)
  • Combined split king size: 76" wide x 80" long (approximately 193 cm x 203 cm)

So, when people ask “What Size Is a Split King Mattress”, the simple answer is:
It has the same overall dimensions as a standard king mattress, but it’s split into two twin XLs.

How Is a Split King Different From a Standard King?

Both a standard king and a split king measure 76" x 80", but there are key differences:

  • Standard king: One single mattress, 76" wide.
  • Split king: Two mattresses, each 38" wide, placed together.

Why does this difference matter?

  • Motion isolation: Each person has their own mattress surface, which can reduce how much movement transfers across the bed.
  • Adjustable bases: Many people choose a split king for independent adjustability, where each side of the bed can be raised or lowered separately.
  • Different firmness per side: With two mattresses, partners can choose different comfort feels if desired.

Will a Split King Fit in My Bedroom?

Since a split king has the same footprint as a standard king, the space considerations are identical:

  • Width: 76"
  • Length: 80"

Before choosing this size, measure:

  • The distance between walls
  • Space needed for nightstands
  • Room to walk around the bed comfortably

A split king usually works best in larger bedrooms, where a king-size bed already makes sense.

What Bedding Do You Need for a Split King?

This is one of the most common follow-up questions to “What Size Is a Split King Mattress”.

Sheets

  • Fitted sheets:
    • Typically, two twin XL fitted sheets (one for each mattress)
  • Flat sheet and covers:
    • Some sleepers use one king-size flat sheet and a shared blanket or duvet
    • Others prefer separate top layers so each person can have their own coverage

Mattress protectors

  • Often, people choose two twin XL protectors, though some use a single king-size protector that covers both mattresses at once.
  • For adjustable bases, separate protectors generally move more smoothly with each mattress.

Do You Need a Special Bed Frame for a Split King?

A split king usually sits on:

  • A standard king-size frame or platform (to support the combined width and length), or
  • Two twin XL adjustable bases placed side by side

The key is that the frame or base must match the total size: 76" x 80".

Most frames that are labeled for a king mattress will also work for a split king, as the outer dimensions are the same. The difference is mainly in how the support is arranged underneath.

Is a Split King the Same as Two Twin Beds?

Not exactly.

  • Two twin beds:

    • Standard twin mattress: about 38" x 75"
    • Two twins side by side: 76" x 75" (shorter than a king)

  • Split king:

    • Two twin XLs, each 38" x 80"
    • Combined: 76" x 80" (true king length)

So a split king gives king-size length, while two regular twins are shorter.

Common Split King Questions

Will there be a gap in the middle?

Yes, there is typically a small gap between the two twin XL mattresses. Some people:

  • Push the mattresses tightly together
  • Use a mattress connector or “bridge”
  • Choose a thicker king-size mattress topper over both mattresses to smooth out the middle

Can I use a headboard with a split king?

Yes. Most standard king headboards are compatible, since they attach to the frame, not the mattress pieces. The headboard simply spans the full 76" width.

Are split king mattresses good for couples?

Many couples choose them because each person gets their own mattress surface, which can:

  • Make it easier to move without disturbing the other person
  • Allow for different mattress types or firmness levels
  • Work well with dual adjustable bases

✅ Quick Mattress Takeaways

Key points consumers should understand about What Size Is a Split King Mattress

  • Exact size: A split king is 76" x 80" overall, made from two twin XL mattresses, each 38" x 80".
  • Same footprint as a king: It takes up the same space as a standard king mattress in your bedroom.
  • Ideal frames: Works with king-size bed frames or two twin XL adjustable bases side by side.
  • Bedding setup: Usually uses two twin XL fitted sheets and either one shared king top sheet/comforter or separate covers.
  • Not two regular twins: Two standard twins side by side are shorter than a split king.
  • Middle gap: There is a slight gap between the mattresses, which some sleepers minimize with a connector or topper.

Understanding “What Size Is a Split King Mattress” helps you plan your room, choose compatible bedding, and decide if this flexible two-piece setup matches how you like to sleep.