Best Split King Size Mattress

Last Updated On February 1st, 2024
Best Split King Size Mattress

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When looking for the best mattress, size is an essential factor—think about available space and who will be using the mattress. Some may prefer a twin bed for their children, while others may want a queen size for more space. An excellent option for couples, particularly couples with differing sleeping preferences, is a split king size mattress.

For the best split king size mattress, consider Amerisleep.

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Amerisleep’s Best Split King Size Mattresses

Quick Guide: A 30-Second Summary

Best Split King Size Mattress Overall Amerisleep AS5
Best Split King Size Hybrid Mattress Amerisleep AS3 Hybrid
Best Split King Adjustable Bed Amerisleep Adjustable Bed+

Our softest and arguably most luxurious model is the AS5 mattress, made with responsive, plush foams for a cloud-like sleeping experience. The AS5 is excellent for couples who want to upgrade their bed.

Mattress Highlights
  • Plant-based memory foam and responsive transition
  • Five zones support the body's different areas
  • Sturdy and supportive Bio-Core® base foam
Recommended For
  • Couples
  • Side sleepers
  • Petite, average, and plus-sized sleepers

The Amerisleep AS5 is our softest model and perfect for side and combination sleepers. It stands at 14 inches tall and contains:

  • 2 inches of Bio-Pur®
  • 2 inches of Active Flex
  • 3 inches of Affinity with HIVE® technology
  • 7 inches of Bio-Core®

The plush feel of each foam layer is designed to cushion the body for maximum comfort without compromising on support. Sleepers can rest easy on the mattress instead of inside it.

Shoppers who prefer bounce in their bed can also try the Amerisleep AS5 Hybrid.

Save $300 on the Amerisleep AS5 with our discount code
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Our AS3 mattress is popular because of its versatility, suiting most body types in different positions. The bouncy AS3 Hybrid also possesses a responsive, airy base for increased comfort.

Mattress Highlights
  • Bio-Pur® memory foam cushions and cradles
  • Pocketed coils keep motions from spreading
  • Soft, breathable mattress cover for airflow
Recommended For
  • Couples
  • Side, back, and combination sleepers
  • Hot sleepers

The Amerisleep AS3 Hybrid is the perfect medium, an excellent choice for side and combination sleepers and, like it’s memory foam mattress counterpart, our most popular hybrid model. It’s 12 inches tall and contains:

  • 3 inches of Bio-Pur®
  • 8 inches of zoned pocketed coils
  • 1 inch of base foam

The AS3 Hybrid provides sleepers with optimal pressure relief in the shoulders and hips through the 3-zoned support system of pocketed coils and contouring Bio-Pur®.

The AS3 is also available as a classic memory foam mattress, perfect for shoppers who want a versatile and affordable mattress.

Save $300 on the Amerisleep AS3 Hybrid with our discount code
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Why Choose Amerisleep?


Bio-Pur® is a plant-based memory foam. During the manufacturing process, castor oil partially replaces petroleum and produces Bio-Pur®, more breathable and responsive than traditional memory foam. Bio-Pur® conforms to the body, relieving pressure points without sinking deeply—sleepers feel like they’re sleeping on the mattress instead of inside it.

Active Flex

Active Flex is a highly responsive foam layer that automatically adjusts to any sleep position. Active Flex is only found inside the AS5 and AS5 Hybrid models, providing extra cushioning in the shoulder and hip areas.

HIVE® Technology

The Affinity layer inside our memory foam models incorporates HIVE® technology—hundreds of hexagonal-shaped segments form a 5-zone support system with a softer feel under the shoulders and hips and a firmer feel under the head, back, and legs. HIVE® technology enables even pressure relief and encourages spinal alignment.

Zoned Pocketed Coils

Inside our AS2, AS3, and AS5 Hybrid models is a support layer of zoned pocketed coils in place of Bio-Core®. Individually-wrapped innerspring coils are formed into a 3-zone support layer with thinner coils for softer support under the head, shoulders, and legs and thicker coils for firmer support under the back and hips. Pocketed coils evenly support the body and provide more cooling through its open structure.


Bio-Core® is the support layer found inside our memory foam models, a durable foam built to last. Bio-Core® evenly distributes body weight across the sleep surface without the risk of sagging.

Base Foam

The base foam is only found inside our hybrid models. Base foam protects the bed frame or floor from pocketed coils and reinforces the top layers of each hybrid mattress.

100-Night Sleep Trial

We offer a 100-night sleep trial with the purchase of any mattress. During this trial period, customers can try out a new mattress within the comfort of their own home. Customers can return the bed free of charge after an adjustment period—we’ll even help you find a place to donate your mattress before issuing a full refund.

20-Year Warranty

Each mattress comes with a 20-year warranty—one of the best in the mattress industry. Our warranty covers any manufacturing defects and sagging greater than an inch. During the first ten years, we’ll repair or replace the mattress free of charge. During the last ten years, we’ll repair or replace the mattress at a prorated charge.

What is a Split King Mattress?

A split king is a king-size mattress split into two separate twin XL beds. A split king mattress provides customized comfort and support for couples—two different mattresses varying in firmness, materials, and layers.

If you don’t see a split king option officially offered, you can still improvise one by purchasing two twin XL mattresses. See our twin XL vs split king mattress guide for more information.

Split King Beds and Adjustable Bases

An adjustable bed base pairs perfectly with a split king mattress. Adjustable frames electronically elevate the head and legs to improve circulation and reduce symptoms of sleep apnea and acid reflux. Plus, adjustable bed frames can set the body in the zero-gravity position to reduce back pain. On split-king adjustable bases, couples can enjoy their own settings without disturbing their sleep partner.

Other features in an adjustable base include under-bed lighting and USB ports to charge electronic devices. Settings are conveniently adjusted via remote control for easy setup and use.

Best Split King Size Mattress

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What to Look for in a Split King Size Mattress

Before buying a mattress, it’s crucial to consider features like mattress type, cooling features, and available sleep trials, return policies, and warranties. Keep your favored sleep position and body type in mind as you browse.

Split Head vs Full Split

A split-head mattress features a partial division in its design, specifically in the upper portion. This split usually extends from the head of the mattress down to approximately the upper third of its length, while the rest of the mattress, including the foot and middle sections, remains undivided.

This partial configuration allows individuals to independently adjust the elevation of the head without affecting the entire mattress, catering to personal comfort preferences. It often works well with an adjustable frame for partners who just want to raise the head of the bed.

On the other hand, a full-split mattress takes the division concept further by completely separating the entire mattress into two distinct sections. Both the head and foot portions are split, creating two separate sleep surfaces. This comprehensive division is excellent for couples who need to build a dual firmness mattress.

Mattress Type

Each type of mattress offers sleepers their own unique feel and set of benefits. Some like the conforming feel of memory foam, while others may prefer the responsive bounce of an innerspring mattress.

Memory Foam

Memory foam gained its popularity through its conforming properties—heat and pressure soften memory foam, causing it to mold to the body and relieve pressure points. Memory foam also provides excellent motion isolation and sleeps silently.

Because of its dense structure, memory foam runs the risk of overheating, but choosing a memory foam mattress with cooling properties reduces this risk.

A memory foam mattress contains a comfort layer of memory foam and a support layer of high-density foam.


Innerspring mattresses are commonly found in households. They provide excellent cooling, bounce, and edge support through innerspring coils. A few drawbacks to innerspring mattresses include less pressure relief due to the thin comfort layer and little to no motion isolation.

An innerspring mattress contains a comfort layer of foam or fiberfill (usually in pillow top form) and a support layer of innerspring coils.


Latex shares similar properties as memory foam—it’s conforming, pressure relieving, and isolates motion well. However, latex is cooler and more responsive than traditional memory foam.

Latex mattresses may contain synthetic or natural latex. Synthetic latex is created through a chemical process, while natural latex is made from rubber tree sap. Natural latex undergoes one of two methods—Dunlop or Talalay.

Dunlop latex is denser and more durable than Talalay. Talalay latex contains polyurethane fillers to give it a softer, more sponge-like feel.

Latex mattresses can be expensive, depending on how much natural latex they contain. A latex mattress contains a comfort layer of latex and a support layer of either high-density foam or latex.


A hybrid mattress combines memory foam and innersprings to form the perfect bed. Hybrid mattresses provide pressure point relief and motion isolation from memory foam, and cooling and bounce from an innerspring. Due to the number of materials they contain, hybrids come at a higher price tag than other mattress types.

A hybrid mattress contains a comfort layer at least 2 inches thick of either memory foam or latex, and a support layer of pocketed coils.

Cooling Features

Those who prefer cooler sleep, especially hot sleepers, will benefit most from cooling features, including plant-based memory foam and innerspring coils.


A significant drawback to traditional memory foam is overheating. To combat this, mattress brands add cooling features, like plant-based oils, gel, and copper or graphite.

  • Plant-based Memory Foam

Plant oils partially replace petroleum during the manufacturing process, resulting in a breathable, more responsive memory foam. Plant-based memory foam has little to no off-gassing odor.

  • Gel Memory Foam

Gel is swirled or mixed in, or gel beads are added during the production process. Gel memory foam absorbs and disperses body heat to regulate temperature.

  • Copper or Graphite Infusions

Both copper and graphite are natural heat conductors—copper pulls heat away and improves local blood flow, while graphite draws heat away from the body and is usually used to cool high-powered machines, like PCs.


Innerspring coils, either on their own or covered in fabric, allow for better air circulation inside the mattress because of their open structure. More airflow pushes heat out and brings in cooler air for temperature regulation.

Sleeping Position

A major factor in finding the best split king mattress is sleeping position. Each sleep position needs a specific firmness level; for instance, stomach sleepers need a firmer mattress to prevent deep sinkage and spinal misalignment.

Side Sleeping

Side sleeping is the most common sleeping position, and also the healthiest. Side sleeping enables better breathing, reduces acid reflux, and improves heart health. To improve spinal alignment, side sleepers can place a pillow between the knees.

The best mattresses for side sleepers are soft to medium in firmness to alleviate pressure points and maintain healthy spinal alignment.

Back Sleeping

Back sleeping is healthy because it naturally aligns the spine. Risks to back sleeping include snoring potential and developing sleep apnea—gravity causes the tongue to fall back, obstructing airways, or the collapse of soft tissue at the back of the throat.

We recommend medium to firm mattresses for back sleepers, as these beds provide enhanced lumbar support and to cradle the hips.

Stomach Sleeping

Stomach sleeping is the unhealthiest and least common sleeping position. Stomach sleeping places large amounts of pressure on the spine, resulting in neck strain and back pain. A thin pillow under the hips relieves pressure and keeps the spine in alignment.

Stomach sleepers need a medium-firm to firm mattress to keep the body resting on the surface and prevent heavy sinkage.

Combination Sleeping

Combination sleepers, or restless sleepers, swap between 2 to 3 sleep positions regularly. They receive the benefits of each sleep position, like better heart health and natural spinal alignment, but they also get the drawbacks, including snoring and back pain.

If you need a comfortable mattress for combination sleeping, consider something medium to medium-firm in firmness, as these offer a balance of comfort and support to maintain spinal alignment.

Body Type

Another major factor in determining the right mattress is body type. The right amount of support keeps the spine aligned, reducing aches and pains, and ensuring better sleep.

Light Sleepers

Light sleepers weigh less than 130 pounds. They need a softer surface to enable contouring and pressure point relief.

Average Sleepers

Average sleepers weigh between 130 to 230 pounds. They sleep best on a medium surface for a balance of comfort and support.

Plus-Size Sleepers

Plus-size sleepers weigh more than 230 pounds. A firmer mattress provides comfort and support without risk of sagging.

Mattress Thickness

When considering a split king, mattress thickness becomes a crucial point of consideration. The total thickness of each twin XL mattress contributes to the overall height and comfort of the split king setup.

Mattresses come in a range of thickness options, commonly between 10 to 14 inches. The choice of thickness depends on individual preferences, body weight, and the desired level of support and plushness.

For couples sharing a split king bed, coordinating the thickness of each twin XL mattress is essential to ensure a seamless and harmonious sleep experience. If one partner prefers a thicker mattress for added plushness, while the other favors a firmer feel with a thinner profile, it’s crucial to find a compromise that meets both preferences.

Sleep Trials, Return Policies, and Warranties

Sleep trials, return policies, and warranties serve to reassure customers of a sound purchase. Each of these policies helps customers find the best mattress and protect that investment for years to come.

Sleep Trial

A sleep trial is an in-home trial period, typically lasting 90 to 120 nights, where customers can try out a new mattress without pressure to buy from a sales associate. If the customer doesn’t like the bed, most mattress companies will issue a full refund. With split king mattresses. both halves may need to be returned.

Return Policy

A return policy is a good substitute if a sleep trial isn’t offered. Return policies generally last 30 days, about the same time it takes for the body to adjust to a new mattress. Should the customer not like the bed, they can return it for a full refund.


A warranty covers any manufacturing defects and sagging greater than 1 inch—this measurement varies, depending on the brand. Most mattresses come with a standard 10-year warranty and only applies to the original purchaser. Warranties don’t cover liquid damage or damage caused through misuse.

Other Mattress Sizes

If a split king mattress size is too big or not the right size for you, take a look at the following sizes to see which one fits your needs.

Twin Size

Twin size mattresses measure 38 inches by 75 inches. They are the smallest standard mattress size with the lowest price point.

Twin beds are perfect for kids and adults with limited living space, like studio apartments. Two twin beds together won’t make a proper split king, as they’ll be a few inches too short. However, two adults may be able to improvise a mattress to share with their twin beds.

Twin XL Size

Twin XL mattresses are the same size as twin beds, except they have 5 inches of extra length, measuring 38 inches by 80 inches. Twin XL beds are great for taller individuals and also fit nicely in smaller spaces. Twin XL mattresses are standard in college dorm rooms.

Full Size

Full size mattresses are 54 inches by 75 inches, leaving more room to sprawl out and get comfy. Full beds are perfect for teenagers, combination sleepers, and single adults.

Queen Size

Queen size mattresses are 60 inches by 80 inches and are the most popular mattress size for single adults living on their own. Queen size beds have plenty of room, both in width and length, for any type of sleeper to stretch.

King Size

King size mattresses measure 76 inches by 80 inches and are the largest standard mattress size on the market—perfect for couples who want more personal space. King-size mattresses are an excellent option for any master bedroom.

California King Size

California king size mattresses have the same area as king-size beds, but are narrower and longer, measuring 72 inches by 84 inches. Cal king beds are an excellent option for taller individuals who need more length from their bed.

Split California King Size

For taller individuals who share their bed with a partner, a split California king size mattress is another good option. A split Cal king mattress is the same size as a Cal king at 72 inches by 84 inches.


Are split king beds comfortable?

Split king beds provide excellent comfort and support, more so than a regular king—two adult sleepers can have their own customized comfort and support, plus since a split king is two separate twin XL beds placed side by side, there’s less motion transfer, reducing the risk of sleep disruptions.

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

Since a split king size mattress is two twin XL beds placed side by side, twin XL fitted sheets with a king-size flat sheet should fit perfectly. Standard king sheets will also work, but these will prevent the mattresses from adjusting independently on an adjustable bed frame. It’s also important to look into sheets for adjustable beds with deep pockets, as this will prevent the sheets from sliding off.

Is a split king bigger than a king?

A split king size mattress is the same as two twin XL beds put together—each mattress measuring 38 inches across for a combined width of 76 inches with 80 inches in length.

How do you keep a split king bed together?

There are a few ways you can keep your split king mattresses from sliding apart: the easiest option is to get a fitted bed frame so the mattresses sit snug in the frame and don’t have any room to move. You can also use one fitted sheet around both mattresses to prevent a gap between the twin XL mattresses (although we do not recommend this for sleepers who want to use a split adjustable bed).

Apart from bed frames and fitted sheets, you can also try non-slip mattress pads and mattress connectors to keep your split king mattress in place.

What is a super king mattress?

Despite their name, super kings are slightly smaller than standard kings, measuring 72 inches by 78 inches. Super kings are still considered “oversized” and are pretty rare, so they often need to be custom made and have a higher price tag.

Is a Split King Size Mattress Right for You?

A split king size mattress allows couples their own mattress space based on their individual sleeping preferences. A split king size bed pairs nicely with an adjustable bed base, providing health benefits like relieving lower back pain. Having one of the best split king mattresses could be the key to better sleep.

About the author

Stacy Liman is a journalism graduate student and a freelance writer with a focus on mindfulness and content marketing. Her passion for understanding and writing about the science of sleep enables her to provide valuable insights into achieving healthier and deeper rest. Stacy's commitment to helping people improve their sleep drives her exploration of new mattresses and sleep-promoting gadgets.

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