Twin XL vs. Split King: What's the Difference? - Amerisleep (2023)

Twin XL mattresses are great for kids and solo sleepers—they offer plenty of legroom and enough space to get comfortable without feeling cramped. Since the dimensions of two twin XL mattresses placed side by side equal that of a king, many mattress brands offer a split-king size.

Split-king size mattresses are two separate twin XL beds placed next to one another in a frame. These beds are perfect for couples with very different sleep needs, as this set-up allows each sleeper to customize their side of the bed.

Twin XL mattresses measure 38 inches by 80 inches, making them 5 inches longer than a standard twin. The extra length comes in handy to accommodate growing teenagers or as mattresses for taller adults. Twin XL sizes are common in children’s rooms, college dorms, guest rooms, and spare bedrooms.

Families with two or more children may benefit from bunk beds that fit twin XL mattresses—optimally utilizing space, leading to more play area.

A twin XL size is also a good option for those living in studio or small apartments where space is limited.

A split king mattress is a standard king divided in half, allowing each sleeper 38 inches by 80 inches of personal space. Split kings allow couples with different sleep styles to customize their side of the bed. If one sleeper wants a soft mattress while another prefers a firm, a split-king allows each sleeper to have their “best mattress.”

Split kings are also a popular option amongst those with adjustable bed frames because they allow couples to adjust each side of the base independently—one partner can sit up and read while the other drifts off to sleep in the zero-gravity position.

To make a king bed look uniform, you’ll need two twin XL fitted sheets and a king-size flat sheet. Split-king sheet sets are not as common, but you can typically purchase these from brands that carry split-king size mattresses.

The first layer of the AS3 is Bio-Pur® foam is airy and adapts swiftly to movements, with a more eco-friendly design than traditional memory foam. We replace some of the usual ingredients inside memory foam with plant-derived oils.

The next layer is Affinity foam with HIVE® technology, a design choice that creates five zones of support. The hexagonal cutouts that make up HIVE® are arranged to increase flexibility under the shoulders and hips, giving these areas more pressure relief. With the Affinity foam’s buoyant transition, this layer increases the surface’s adaptability.

The base foam is Bio-Core®, a strong foam that creates a sag-resilient structure.

Enveloping the mattress’s layers is a cover of Refresh fabric, a material that takes body heat and transforms it into infrared energy. This energy then penetrates the body and can boost local blood flow for a restorative feel.

The Amerisleep AS3 ships free and comes with a 100-night sleep trial and a 20-year warranty.

How Does a Twin XL Size Relate to a Split King?

A standard king size mattress divided in half is two twin XL beds, measuring 38 inches by 80 inches—creating a split king bed. A split king is not a different size in itself, it’s two twin XLs placed side by side on a bed foundation.

While twin XLs can be used only as single beds, split kings (two twin XLs) are the perfect mattresses for couples with different sleep needs.

Is a Twin XL or Split King Mattress Better?

Size of Your Bedroom

King mattresses, no matter how they’re constructed, will take up a significant amount of room.

Mattress Budget

Naturally, a smaller mattress is going to cost less than a larger one.

Sleeping Alone or with a Partner?

If you plan on sleeping by yourself for the foreseeable future, it doesn’t make much sense to buy a split king mattress. This bed works best as a mattress for couples when you know what each partner finds comfortable in a bed. A split king bed also establishes one of the best mattresses for motion isolation, as being separate mattresses keeps your movements from jarring your partner out of sleep.

Other Mattress Sizes

If a twin XL or split king mattress doesn’t suit you, check out other available sizes such as a twin, full, queen, king, or California king.

Twin Size

Measuring 38 inches by 74 inches, twin size mattresses are perfect for children, or single adults. Twin beds are small in size, making them a convenient option where space is limited.

Twin size mattresses are also compatible as bunk bed mattresses. If you have two or more children, you can utilize space with a bunk bed.

See also:

  • Twin vs Full vs Queen Mattresses
  • Twin vs Twin XL Mattresses
  • Single vs. Twin Bed Size Mattresses

Full or Double Size

A full or double bed is 16 inches wider than a twin and may accommodate an adult and a child. Measuring 54 inches by 75 inches, a full size mattress is commonly found in children’s rooms, guest rooms, college dorm rooms, or shared adult bedrooms. Though called a “double,” ironically, this size may be too small for couples.

Queen Size

Queen mattresses are the most popular amongst Americans because they suit single sleepers as well as couples. Measuring 60 inches by 80 inches, they are best for single adults offering them more room to stretch and sleep comfortably. However, a queen may be too small for some couples who prefer their personal space.

A queen size is perfect for single sleepers because they can stretch out and relax without the fear of rolling off the bed. If you are a single sleeper, with no constraint of space or budget, a queen may be a good fit for you.

See also:

  • Queen vs Twin XL Matresses
  • King vs Queen Mattresses

King Size

Measuring 76 inches by 80 inches, the king size mattress is a perfect fit for couples. A traditional king is big enough to accommodate children—if they want to sleep with their parents on some nights. Aking size bed, while suitable for larger master bedrooms, is expensive and heavy—maneuvering a king bed may be difficult due to its weight.

California King Size

A California king size mattress is 4 inches narrower and 4 inches longer than a king. Measuring 72 inches by 84 inches, a California king is the longest available standard size mattress—the extra length gives more legroom for tall people who might have feet hanging off the side of a standard king bed.

See our comparison guide of king vs California king mattresses.

Mattress Dimensions Suitable to Room Sizes

An overcrowded bedroom may disturb your sleep. When buying a bed, factor in conditions like furniture and floor lamps, and leave enough room for walking space. We suggest leaving 2 feet of space on all three sides of your bed to provide a peaceful sleeping ambiance without feeling overcrowded.

Twin XL vs. Split King: What's the Difference? - Amerisleep (1)

More to Consider for Comfort

Mattress Firmness

Understanding how mattress firmness affects how a mattress feels to you can help you choose the best mattress for your body type and sleep position. Here’s a quick run-down of how to choose the right firmness:

  • Mattresses for side sleeping
  • Mattresses for back sleeping need a balanced feel to ease pressure and support the spine. Medium-firm is generally best, though some will enjoy medium or true firm feels.
  • Mattresses for stomach sleeping should offer a firm feel to offset the sinkage that can cause back pain.
  • Mattresses for combination sleeping
  • Mattresses for lightweight sleepers
  • Mattress for heavy people

Mattress Type

Mattress Thickness

The thickness of a mattress is often overlooked when it comes to a bed’s expected comfort. However, the simple fact is that a thicker mattress


Do two twin XL beds make a California king mattress?

No, two twin XL beds together will make a standard king mattress. Two twin XL mattresses placed side by side will measure 76 inches by 80 inches (size of a standard king), while a California king is 72 inches by 84 inches. Split California king mattresses do exist, but they are less common than a traditional split king bed.

Do you need a box spring on an adjustable bed?

No. Box springs cannot bend like an adjustable base, so you cannot pair the two. Adjustable bed frames do not require box springs or foundations since they provide a solid, sturdy support for your mattress. Split king mattress can be kept directly on a split king adjustable bed frame for more personalized comfort. Adjustable bed bases can be elevated at the head and feet to better relieve pressure points.

Who needs a split king bed?

Split king beds are perfect for couples who have different sleep needs and prefer different mattress types. Partners may require a different combination of cushion and support for their comfort. They can have a latex, memory foam, innerspring or hybrid mattress on either side of the bed. To maintain a uniform look, it’s better if both the twin XL mattresses are of the same height.

What kind of sheets do you put on a split king bed?

Typically, you would buy a split king sheet set that has two twin XL fitted sheets and a king size flat sheet. It is possible to cobble together a split king sheet set from twin XL and standard king sheets, but it is more expensive than buying a split king size set. Aside from the fitted sheets, which must be twin XL, you would also use other king size bedding, from toppers to pillows and blankets.

Can I use an adjustable bed with a twin XL or split king?

Yes, twin XL and split king size adjustable beds are both quite common. Split king adjustable beds can typically be set up to move as one unit or to let each side be adjusted individually. Twin XL adjustable beds are typically the smallest size that can be bought; standard twin adjustable beds do exist but they are quite uncommon.


When deciding on your mattress size, consider your sleeping style, whether you sleep alone or with a partner, and your budget. A twin XL size may suit a single sleeper, but for couples, a split king bed isperfect. A split king might be the better choice if you and your partner prefer different mattress types and have different sleep needs.

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