Twin XL vs. Split King: What’s the Difference?

Last Updated On April 11th, 2024
Twin XL vs. Split King: What’s the Difference?

Key Takeaways

  • Twin XL Mattresses: Twin XL mattresses are longer than standard twin mattresses, measuring 38 inches by 80 inches. They are suitable for children, teenagers, or taller adults. Twin XLs are commonly found in children’s rooms, college dorms, guest rooms, and small apartments.
  • Split King Mattresses: A split king mattress is created by placing two twin XL mattresses side by side, resulting in a size equivalent to a standard king (76 inches by 80 inches). Split king mattresses are ideal for couples with different sleep preferences, as they allow each sleeper to customize their side of the bed. These mattresses are also popular with adjustable bed frames.
  • Choosing the Right Size: The choice between a twin XL and split king mattress depends on factors like the size of your bedroom, your budget, whether you sleep alone or with a partner, and your individual sleep preferences. Consider your comfort, room size, and mattress firmness when making your decision.

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.

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What Is a Twin XL Size?

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 mattress is also a good option for those living in studio or small apartments where space is limited. When it comes to sharing a bed, two adults can’t sleep comfortably on a twin bed. However, that’s if there’s only one twin bed available, and not two pushed together to make a split king.


  • Suitable for growing teenagers and tall adults
  • Lightweight, easy to carry
  • Bunk bed compatible
  • Longer than a standard twin


  • Too small for couples
  • Not suitable for co-sleeping with pet or child

Prices of our Amerisleep Twin XL Size Mattresses

Amerisleep AS1$699
Amerisleep AS2$899
Amerisleep AS3$1099
Amerisleep AS3 Hybrid$1299
Amerisleep AS4$1099
Amerisleep AS5$1699
Amerisleep AS5 Hybrid$1999
Amerisleep Organica$1099

What Is a Split King Size?

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.

For example, if one sleeper wants a soft mattress while another prefers a firm, a split-king allows each sleeper to have their “best mattress” by creating a dual firmness mattress. This is not to be confused with an adjustable firmness mattress, which allows you to change up the firmness on the fly.

A dual firmness mattress often has each side of the bed with a set-in-stone firmness, but each half caters to a partner’s preferences.

Twin XL vs. Split king

Aside from accommodating different sleeping preferences, 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. With a split king adjustable bed for couples, 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.


  • Personalized comfort and support
  • Lightweight
  • Easy to maneuver


  • Expensive
  • Difficulty finding sheet sets

Prices of our Amerisleep Split King Size Mattresses

Mattress Price
Amerisleep AS1$1398
Amerisleep AS2$1798
Amerisleep AS3$2198
Amerisleep AS3 Hybrid$2598
Amerisleep AS4$2198
Amerisleep AS5$3398
Amerisleep AS5 Hybrid$3998
Amerisleep Organica$2398

Best Amerisleep Mattresses

Quick Guide: A 30-Second Summary

Best Mattress Overall Amerisleep AS3
Best Soft Mattress Amerisleep AS5 Hybrid
Best Natural Mattress Amerisleep Organica

The Amerisleep AS3 is our most popular mattress, with a medium feel that suits single adults interested in a twin XL or couples who want to share a split king size mattress.

Mattress Highlights
  • Plant-based memory foam comfort
  • Buoyant transition with targeted support
  • Sag-resilient base foam
Recommended For
  • Side, back, and combo sleepers
  • Hot sleepers
  • Couples seeking a versatile split king

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.

Save $450 on the Amerisleep AS3 with our discount code
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Mattress Higlights
  • Mattress cover promotes restoration
  • Soft memory foam and bouncy transition
  • Pocketed coils increase responsiveness
Recommended For
  • Side sleepers
  • Petite sleepers
  • Couples who want a hug-like mattress
Save $450 on the Amerisleep AS5 Hybrid with our discount code
Shop Now
Mattress Highlights
  • Organic cotton and wool flame barrier
  • Latex foam layers for comfort and transition
  • Motion-isolating pocketed coil support
Recommended For
  • Most sleeping styles
  • Sleepers with non-latex allergies
  • Hot sleepers
Save $450 on the Amerisleep Organica with our discount code
Shop Now

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

Eastern king mattresses, no matter how they’re constructed, will take up a significant amount of room. If you plan on having a king size bed frame, make sure you have adequate walkway space and room for added bedroom furniture.

Mattress Budget

Naturally, a smaller twin mattress for a space like a studio apartment bedroom 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, allowing you to build a dual firmness mattress that can suit two tastes.

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 a California king bed.

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:

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 bed,” ironically, this size may be too small for couples. Each partner would have a sleeping space roughly the size of a crib mattress on a full size bed.

See also:

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. A queen bed fits in a small bedroom nicely, much more easily than a king bed, too. If you are a single sleeper, with no constraint of space or budget, a queen may be a good fit for you.

See also:

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. A king 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.

Occasionally, you will also see split California king beds. These are less common than standard split kings, as a split California king bed has two sides that are 36 inches by 84 inches rather than two separate twin XL mattresses. However, a split California king mattress can be excellent for adjustable beds and as mattresses for tall people.

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 size, 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.

Mattress Dimensions Bedroom Size

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 should have a soft to medium firmness that will contour to the sleepers’ shoulders and hips to relieve pressure while supporting proper spinal alignment.
  • 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 should have a medium to medium-firm feel with some responsiveness that will adjust to different sleep positions while continuing to support the body.
  • Mattresses for lightweight sleepers should be in the softer range of their sleeping position, to more readily conform to a smaller body.
  • Mattress for heavy people should conversely be at the firmer end of a position’s range, to withstand the additional weight.

Mattress Type

There are four main types of mattresses to consider:

  • Memory foam mattresses consist of polyurethane foam that softens in reaction to body heat and pressure to mold to a sleeper’s shape and provide customized support.
  • Latex mattresses are naturally firm, resilient, and contouring, providing good support for the body and spine while also having some bounce.
  • Innerspring mattresses contain steel coils or springs to provide support and bounce, allowing the mattress to conform to body curves while also maintaining structure.
  • Hybrid mattresses combine the supportive springs of an innerspring mattress with the contouring comfort of memory foam or latex to deliver excellent overall sleep comfort and minimal motion transfer.

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 typically has more cushion, support, and durability. That does not mean a thicker mattress is always the better option, though, as a bed frame’s weight limit must also be considered.


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 in their twin XL bed 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 sheets, you would also use other king size bedding for your split king size bed, 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 mattress may suit a single sleeper, but for couples, a split king bed is perfect. A split king might be the better choice if you and your partner prefer different mattress types and have different sleep needs.

About the author

Mitchell Tollsen is a graduate student and a freelance writer who’s contributed to the Early Bird blog for three years. Mitchell’s always been fascinated by the science of sleep and the restorative processes our bodies undergo when at rest. The self-titled “Sleep Expert” is always looking for ways to improve his shut-eye, and throughout the years has implemented numerous lifestyle changes and tried dozens of sleep-promoting gadgets to determine the best ways to truly get better rest.

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