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

If you’re wondering “What size mattress is a split king?”, you’re likely trying to figure out if it will fit your bedroom, your bed frame, or your bedding. This guide walks through the exact dimensions of a split king, how it compares to other sizes, and what you should know before choosing one.

What Size Mattress Is a Split King?

A split king is essentially two separate twin XL mattresses placed side by side on the same frame.

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

That means a split king is the same overall size as a standard king mattress, just divided into two pieces instead of one solid surface.

Why Do People Choose a Split King Instead of a Regular King?

Although a split king and a king measure the same overall size, the sleeping experience can feel different.

Common reasons people choose a split king include:

• Independent feel on each side – Each person has their own mattress surface.
• Less motion transfer between partners – Movement on one side may be less noticeable on the other.
• Easier to move and set up – Two twin XL mattresses are lighter and easier to carry than one large king.
• Compatible with adjustable bases – Many adjustable bed setups use two twin XL bases side by side.

In short, a split king offers the space of a king with extra personalization on each side.

How Does a Split King Compare to Other Mattress Sizes?

Here’s a simple comparison to help place “What size mattress is a split king” in context:

The key takeaway: a split king is not bigger than a king; it’s just divided into two twin XL mattresses.

Do You Need Special Bedding for a Split King?

This is one of the most frequent follow-up questions after “What size mattress is a split king?”

Fitted Sheets

Because a split king uses two twin XL mattresses, most people use:

• Two twin XL fitted sheets (one for each mattress)

This allows each side to move independently—especially useful if you have an adjustable base.

Flat Sheets and Blankets

You have two basic options:

• One king-size flat sheet and one king blanket/comforter shared across both sides
• Two separate twin XL blankets/duvets, one for each side, for more individualized comfort

Both options can work; it comes down to preference for shared versus separate bedding.

Will a Split King Fit My Existing King Bed Frame?

If you already own a standard king bed frame, it will typically accommodate a split king, because:

• The total dimensions are the same: 76" x 80"
• The frame usually supports the outer edges, with slats or a platform underneath

However, pay attention to:

• Center support: Some frames use a center beam. With a split king, the two twin XL mattresses will rest on either side of it.
• Box spring or foundation needs: Some setups use two twin XL foundations instead of one king foundation.

If your frame is designed for a king mattress, it usually works for a split king as well, but checking the support structure avoids surprises.

Are There Any Downsides to a Split King?

While a split king offers flexibility, a few common concerns come up:

• The center gap: There will be a seam where the two twin XL mattresses meet. Some people barely notice it; others use a fitted king mattress topper or a “gap filler” accessory to smooth it out.
• Different mattress feels: If each side uses a different firmness or material, the center may feel slightly uneven when lying across both.
• Bedding setup: You’ll need twin XL fitted sheets instead of one king fitted sheet.

For many couples, these tradeoffs are worth the customization and ease of use a split king offers.

How Do I Know If a Split King Is Right for My Room?

When thinking beyond “What size mattress is a split king” to “Will it fit my space?”, consider:

• Room size: A split king takes up the same floor space as a king. If a king fits comfortably, a split king will too.
• Doorways and stairs: Two twin XL mattresses are easier to maneuver through tight spaces than a single king.
• Adjustable base plans: If you’re considering an adjustable bed, many setups are designed around a split king configuration.

📝 Tip: Measure your room and allow extra space on all sides for walking, nightstands, and opening drawers or doors.

✔️ Quick Mattress Takeaways

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

• A split king equals two twin XL mattresses placed side by side.
• Each twin XL is about 38" x 80", giving a combined size of 76" x 80", the same as a standard king.
• Split king and king have identical total dimensions; the difference is that a split king is divided into two pieces.
• You’ll typically use two twin XL fitted sheets and either one king flat sheet/comforter or two separate blankets.
• Most king bed frames can hold a split king, since the outer dimensions are the same.
• The main advantages are independent feel on each side, easier moving, and compatibility with many adjustable bases.
• The main tradeoff is the center gap between the two mattresses, which some people address with a topper or connector.

Understanding what size mattress is a split king helps you plan your space, choose proper bedding, and decide whether this flexible setup matches how you like to sleep.