Best King Size Mattress in a Box: Reviews and Buyer’s Guide

The mattress in a box trend has revolutionized the mattress industry. Beds are compressed and shipped directly to your doorstep and are set up in minutes. There is no need to visit a mattress retailer or deal with sales associates. Now, you can shop online and get a high-quality mattress shipped right to your home. By sending their products directly to you, online mattress brands cut overhead costs and offer you a much lower price than what you might find at a mattress store.

Beds of all sizes are shipped in a box, including king size mattresses. Although a king is the largest standard size mattress, measuring 80 inches long and 76 inches wide, online brands compress them in a way that makes them easy to ship. Once it arrives at your door, you simply unwrap it and let it expand, and you are ready to start getting a better night’s sleep.

A king size bed is a luxurious and comfortable sleep space. Maybe you’re a solo sleeper who needs more legroom, or you and your spouse prefer more space. —a king may be the perfect size for you. When upgrading to a king, a mattress-in-a-box can make the shopping process much easier. To help you along the way, we outline some of the best king size mattress-in-a-box options. We also offer some points to consider when selecting the best bed.

Best King Size Mattress in a Box of 2023

	Mattress	Highlights	Price (Queen)
	Amerisleep AS3	Features Amerisleep’s unique plant-based memory foam, Bio-Pur®, which is non-toxic and eco-friendly	$1699
	Amerisleep AS5 Hybrid	Pocket spring coil base is zoned to provide the perfect amount of cushioning and support	$2299
	Zoma Mattress	Gel-infused memory foam wicks heat and moisture away from the body	$799
	Zoma Hybrid	Reinforced edge support to reduce motion transfer and make movement on the bed more comfortable	$1099
	Vaya Mattress	Two hypoallergenic foam layers provide a balance of compression and support	$799
	Nolah 10"	AirFoam™ comfort layer relieves pressure without trapping unwanted heat	$1399
	Purple® Hybrid Mattress	Purple Grid™ provides no-pressure support and cushions joints	$1999
	Tuft & Needle Mint	Graphite infused poly-foam for a clean, germ-free sleep surface	$1145

1. Amerisleep AS3

Amerisleep’s AS3 is their most popular mattress due to its universal comfort level suitable for most sleep positions and body types. The medium firmness is soft enough to cushion joints when side sleeping, but it also has a slight firmness to reduce sinking so the spine doesn’t bow.

The cover of the AS3 is made with an ultra-soft, breathable fabric to prevent heat buildup. This removable cover is also machine-washable, so you enjoy a clean, germ-free sleep every night.

The top layer of the AS3 features Amerisleep’s unique plant-based memory foam, Bio-Pur®. This foam has fewer petroleum-based oils and more plant-based oils than standard memory foam, making it non-toxic, eco-friendly, and lightweight. Plus, Bio-Pur® is highly responsive and molds to the curves of your body with pressure-free support.

A layer of Amerisleep’s Adaptive foam with HIVE® technology sits in the middle of the mattress. HIVE® offers the perfect compression level to sensitive joints, so you never develop painful pressure points. This layer is zoned to be firmer along the back to keep the lumbar spine supported and in alignment with the shoulders, so you wake with less pain.

The base of the AS3 features a strong, durable, support foam to prevent sagging and indentations.

All foam layers of the AS3 are backed by a CertiPUR-US® certification, guaranteeing the bed is free of harmful chemicals or flame retardants. This certification ensures minimal off-gassing, or “new mattress smell,” when the bed is brought indoors.

As with all Amerisleep mattresses, the AS3 comes with a 20-year warranty covering manufacturing defects such as sagging. You can test out the feel and support of the AS3 with Amerisleep’s 100-night sleep trial period.

2. Amerisleep AS5 Hybrid

Amerisleep now offers three hybrid mattresses. If you prefer a softer bed with a slight bounce, the Amerisleep AS5 Hybrid may be perfect for you.

The AS5 Hybrid has the same lightweight, airy cover as the AS3. This cover keeps the surface of the mattresses cool and inviting.

The Bio-Pur® comfort layer in the AS5 Hybrid has an ultra-soft feel and contours to the body so muscles completely relax and recover. Although soft mattresses often cause sleepers to feel “stuck,” making it difficult to move around, the AS5 Hybrid has a buoyancy to prevent this.

The second layer of this hybrid features Amerisleep’s Active Flex foam. Active Flex has a natural elasticity to keep the body lifted and aligned, so you wake feeling refreshed and ready for the day.

The AS5 Hybrid has a base made with pocketed spring coils. Each coil is zoned to respond to pressure differently. Near sensitive joints, such as the hips and shoulders, these coil springs are thinner and easily compressed to reduce pressure points. Along the back, coils are thicker and more supportive to ensure the spine stays neutral.

To determine if the AS5 Hybrid is right for you, you can test it out risk-free with Amerisleep’s 100-night sleep trial. The AS5 Hybrid also comes with a 20-year warranty covering manufacturing defects and sagging below .75 inches.

3. Zoma Mattress

The Zoma is an excellent mattress for athletes and other active individuals. Each layer promotes deep relaxation, so sore and tired muscles heal and rebuild.

The Zoma cover is made with a soft, stretch-knit fabric that molds to the body. This cover is ventilated to keep air moving across the bed’s surface, so you sleep cool and throughout the night.

The top layer features Zoma’s gel-infused memory foam with Triangulex™ technology. While the gel infusion pulls away heat and moisture, the Triangulex™ cutouts keep the hips and shoulder from sinking and focusing the spine out of alignment.

The transition layer of the Zoma is made with their Reactiv™ foam—a latex-like material to prevent sinkage and reduce motion transfer. The combination of Reactiv™ foam and the soft memory foam top layer promote deep sleep and muscle recovery.

The base features Zoma’s Support+ foam, a stable, durable material to reduce sagging, so the mattress supports you for years.

To guarantee your satisfaction, Zoma includes a 10-year warranty and a 100-night sleep trial with each of their mattresses.

4. Zoma Hybrid

Zoma’s Hybrid mattress is similar to their memory foam model. However, this mattress has a support system made with spring coils that give it a bounce similar to traditional innerspring beds. For those who prefer the lift and responsiveness of a coil mattress and want the pressure-relief of foam, the Zoma Hybrid is a great choice.

Like their memory foam mattress, the Zoma Hybrid has a stretch-knit cover and a gel-infused memory foam comfort layer. These materials work to regulate temperature and prevent heat-trapping, so you sleep soundly throughout the night.

Zoma’s Reactiv™ foam acts as the barrier between the top layer and the spring coil base. This material lifts and aligns the body with no-pressure support, helping you sleep in a safe, neutral position.

The coil base in the Zoma Hybrid is more advanced than those found in a traditional innerspring mattress. The coils are pocketed for added comfort and more independently of one another—allowing each coil to respond more accurately to pressure. The bed’s perimeter is also reinforced with edge support, making getting in and out of bed more comfortable.

A 100-night risk-free and 10-year warranty comes with each Zoma Hybrid.

5. Vaya Mattress

If you are looking for an affordable king size mattress-in-a-box, the Vaya is a great option. This bed has two hypoallergenic foam layers and is available at a budget-friendly price, with the king Vaya costing just $799.

The cover of the Vaya Mattress is made with an ultra-soft, perforated material to increase breathability. The comfort layer is called Vaya Comfort Foam. This foam contours to the body for maximum comfort and support without trapping heat.

However, the Vaya Comfort Foam has a buoyancy perfect for keeping the body lifted and the spine resting in a safe, neutral position. Vaya foam also has an advanced open cell structure to retain less heat, so the surface always stays cool to the touch.

The base layer of the Vaya features a stable support foam to reduce sagging and structural defects. You can place this mattress on most modern bed frames without worrying about damage—this includes adjustable bases and slatted foundations.

Vaya includes a 10-warranty to protect your investment and a 100-night sleep trial, which allows you to test out the bed for yourself.

6. Nolah Original

The Nolah Original is a 10-inch mattress with a medium comfort level suitable for most sleepers. This bed also has several cooling features for those who sleep hot.

The cover of the Nolah Original is made with a soft and luxurious viscose material. This cover is super absorbent and designed to wick away heat and moisture.

The comfort layer of the Nolah is made with 2 inches of their proprietary AirFoam™—a durable, poly-foam material that contours to the body without trapping heat. According to their website, the AirFoam™ can relieve pressure in the hips, shoulders, and back four times better than most mattress foams. It also has an elastic quality to keep sleepers resting on top of the mattress.

A 1-inch transition layer sits beneath the comfort layer. The foam provides protection against sinking and helps improve motion isolation.

The base of the Nolah Original holds 7 inches of their high-density foam to support the soft layers above and prevent sagging. Nolah’s base is also durable and increases the lifespan of the bed.

With each mattress, Nolah offers free shipping and free returns. They also include a 120-night sleep trial and a 15-year warranty.

7. Purple® Hybrid

Purple® is another popular mattress-in-a-box brand known for their unique Purple Grid®. The Purple® Hybrid combines this grid, two layers of poly-foam, and a spring coil support base to deliver no-pressure support.

The Purple® Hybrid Mattress cover is made with their StretchMax material, which is soft and cozy, yet breathable. This cover pushes warm air out through the side panels of the mattress to prevent heat retention.

Two inches of the Purple Grid™ sit beneath this cover. This grid is made with a resilient Hyper-Elastic Polymer®, a material that flexes under intense pressure to keep you supported throughout the night. The grid is also soft and conforming, so sleepers are less likely to develop pressure points.

The Purple® Hybrid support base features 7.5-inch pocketed spring coils to add durability and support to the mattress. These coils mold to the curves of the body to prevent sinking and spinal misalignment.

Every Purple® Mattress comes with a 10-year warranty and a 100-night sleep trial to ensure you are happy with the overall support and feel of the bed.

8. Tuft & Needle Mint

Tuft & Needle made a name for themselves as one of the first mattress-in-a-box companies. Now, they offer three different mattresses—two all-foam beds and a hybrid model. We recommend their Mint Mattress because it has two comfort layers to cushion and protect the joints from pressure points.

Beneath a lightweight, stretch-knit cover, the first comfort layer features Tuft & Needle Adaptive foam with a graphite infusion. Since graphite is a natural heat conductor, body heat passes through this foam without changing the bed’s temperature.

The second comfort layer is made with a responsive poly-foam infused with gel microbeads. The gel infusion provides more protection against overheating by absorbing warm air and pushing it out the mattress’s sides. The responsiveness of the layer also prevents sinkage.

The Mint’s base layer features a durable support foam to reduce sagging and keep you supported through years of use. Tuft & Needle offers a 10-year warranty and a 100-night sleep trial.

SEE ALSO: Most Comfortable Mattress

SEE ALSO: The Best Place to Buy a Mattress & 7 In-Store Myths

What is a Mattress in a Box?

As you shop for a mattress online, you may come across the terms “mattress in a box” or “mattress in a box.” These terms refer to mattresses compressed and rolled into a box, then shipped directly to customer’s homes.

Most mattress in a boxes have a similar construction as those found at brick and mortar locations; however, online beds are much more affordable. By cutting out the middleman and shipping directly to their customers, these brands save money, which is reflected in their low prices.

Why Buy a Mattress in a Box?

In addition to a budget-friendly price,  mattresses in a box come with the following benefits:

• Free shipping: Most reputable online mattress retailers offer free shipping and free returns. Combined with the sleep trial, free shipping makes buying a mattress in a box risk-free.
• No sales associates: When shopping at a brick and mortar mattress store, sales associates may make you feel pressured to make a purchase. When shopping for a bed online, you have the freedom to shop around and do your research without feeling rushed.
• Longer sleep trial: Online mattress brands offer generous sleep trial periods allowing you to sleep on the mattress in the comfort of your own home. If the bed is not right for you, most companies exchange the bed or provide a full refund. It can often take 4 to 6 weeks to become acclimated to a new bed, so a sleep trial is essential to make sure the mattress is supporting you correctly.
• Transparent warranty: When purchasing a mattress from a brick and mortar store, the retailer is typically not authorized to answer questions or make claims related to the bed’s warranty. This is because the warranty runs through the manufacturers and not the retailer. When purchasing a bed directly from the brand, the warranty terms are much more transparent and straightforward. Plus, if you have any issues with the mattress, it is easier to contact the company directly.

Who Are King Size Mattresses Right For?

Most couples prefer a queen or king size mattress. A queen size mattress measures 60 inches wide by 80 inches long. Although king size beds also measure 80 inches long, kings measure 76 inches wide, which gives couples 38 inches of personal space. Couples who prefer more room to stretch out or those whose children frequently climb into bed with them may prefer this additional width.

However, king size mattresses require more space, so be sure your bedroom can accommodate this larger size bed. Standard size bedrooms measure 11 by 12 feet (132 square feet), and king size beds are often too big for this size of room. However, a master bedroom, measuring 14 by 16 feet (224 square feet), should accommodate a mattress for couples well. Each partner should have plenty of space to maneuver around a king size bed .

What to Consider When Buying a Mattress in a Box

Before deciding on the best mattress for you, there are a few other factors you should consider. In addition to size, you should determine the firmness and mattress type most suited to your body type and sleep position.

Mattress Type

The type of materials and layers in a mattress determines its firmness and durability. To help you decide which type might work best for you, we break down the details of the four most common mattress types below.

Memory Foam Mattresses

Memory foam is a highly responsive material that contours to the body for maximum support and pressure relief. When resting on memory foam, the muscles completely relax so you experience deeper, more restorative sleep. Memory foam mattresses are perfect for athletes and those who live with chronic pain.

Memory foam is typically used in the top layer of the mattress, while a sturdier foam is used in the mattress base. These beds are also very durable and last up to 10 years. The memory foam used in the comfort level can be made in several different firmness levels, from soft to firm—making it easy to find a memory foam bed for your needs.

The biggest complaint regarding memory foam is its tendency to trap heat. Therefore, be sure to purchase a memory foam mattress with cooling features, such as plant-based memory foam or gel-infused memory foam. These additions improve airflow across the surface of the bed and regulate body temperature.

To make sure your new foam mattress is safe and free of toxic flame retardants, look for foam varieties certified by CertiPUR-US®. This certification ensures the bed was not made with any harmful chemicals.

Latex Foam

Latex foam mattresses have a natural buoyancy because this foam is derived from rubber tree sap. The bounciness makes it an ideal mattress material because it helps prevent over sinking and spinal misalignment. Back sleepers and heavier sleepers enjoy the even weight distribution and slight bounce of latex.

Like memory foam, latex mattresses are available in several firmness levels. The manufacturing process can change the feel of the foam. However, most latex foam mattresses have a medium to medium-firm feel.

Latex foam is also one of the most durable mattress materials, with most latex beds lasting between 12 and 15 years. Latex is also naturally resistant to bacteria, viruses, and dust mites.

Hybrid Mattresses

Hybrid mattresses have a 2 to 3-inch foam comfort layer and a support system made of spring coils. Most hybrids feature pocketed coils, which respond more accurately to pressure than traditional spring coils.

The foam top layer offers sleepers contouring and pressure relief, while the coil base keeps the body lifted on the mattress to promote a safe, neutral spine. Heavier individuals (those 230 pounds and up) typically prefer a hybrid bed because it prevents the feeling of being “stuck” in the mattress, making it easier to change positions during the night.

Depending on the type of foam used in the comfort layer, hybrids may have a plush, soft feel, or a firm feel. Hybrids made with high-quality memory foam or latex foam last between 8 and 10 years.

Innerspring Mattress

Innerspring mattresses have been a staple for many years. Foam and hybrid mattresses have become popular in recent years, for their pressure-relieving abilities. However, because many people have become accustomed to the bounce of a spring coil bed, innerspring mattresses remain popular today.

These beds have a comfort layer made of cotton, wool, or foam. The top layer on an innerspring bed is often thinner than on most hybrids. Combining a thin comfort layer and a thick innerspring base causes these beds to feel medium-firm to firm, which may not work well for side sleepers, lightweight sleepers, or those with chronic pain.

The firmness of an innerspring bed often results in painful pressure points for many sleepers. Most people rest more comfortably on a memory foam, latex foam, or hybrid mattress, as they provide more pressure relief.

Innerspring beds also have a shorter lifespan, with most of these beds lasting 6 to 8 years. Traditional coil springs break and bend easily. This creates lumps and indentations in the mattress, which may leave you feeling unsupported and cause pressure points.

If you prefer more bounce, we recommend a hybrid mattress. These beds give you the same buoyancy as a traditional spring coil bed, but with contouring and pressure-relieving properties. Pillow-top mattresses, a type of innerspring bed with a thicker comfort layer, may also be suitable. However, be sure the topper has at least 2 to 3 inches of foam.

Firmness and Sleep Positions

Your sleep position and body type determine the mattress type and firmness right for you. Resting on a bed that is soft or too firm for your needs can leave you with aches and pains in the morning. Over time, incorrect firmness may lead to sleep disruptions and chronic pain.

Mattress firmness is typically rated on a scale of 1 to 10—1 being the softest and 10 being the firmest. However, this scale varies by brand, so be sure you understand the exact firmness you are getting before purchasing a new bed.

Below, we break down the most common sleep positions and explain the firmness and mattress type best for these sleepers.

Side Sleepers

Resting on your body’s side often causes tension to build-up near the hips and shoulders. Therefore, side sleepers need a soft to medium mattress firmness to cushion and protect the joints from pressure points. Memory and latex foam and hybrid mattresses tend to work best for these sleepers.

To find the best mattress for side sleepers, check out other guide. 

Back Sleepers

Resting on your back is one of the safest sleep positions because it reduces pressure on the hips and shoulders. However, if your mattress is too soft, the hips may sink too far into the bed and force the spine to bow. Resting in this awkward position every night may lead to constant pain in the lumbar spine (lower back).

The best mattress for back sleepers evenly distributes body weight so muscles fully relax and the spine remains neutral. A medium to medium-firm mattress works best for back sleepers. Heavier back sleepers may prefer a hybrid mattress with a medium-firm foam topper or a latex mattress. Lightweight sleepers and side sleepers often prefer a medium memory foam mattress or a hybrid with a medium comfort layer.

Stomach Sleepers

When resting on your stomach, the hips and head arch upward, exaggerating the spine’s natural curve. This position causes the muscles in the back to tighten, leading to tension and pain. Therefore, we suggest avoiding stomach sleeping when possible. However, if this is your preferred sleep position, we recommend firm mattresses for stomach sleeping. A firmer comfort level keeps the hips level and minimizes the spine’s curve to alleviate pressure.

Stomach sleepers may benefit from a firm latex mattress or a hybrid with a firm foam comfort layer.

Combination Sleepers

If you toss and turn during the night, a medium mattress is best for you. This comfort level is soft enough to cradle the joints and reduce pressure points when sleeping on the side. A medium mattress is also soft enough to support the lower back and evenly distribute weight when back seeping.

Warranty and Sleep Trial

As we mentioned above, mattress in a boxes come with a generous sleep trial period and warranty to ensure you are happy with the bed. Below, we explain what to look for when determining a good mattress warranty and trial period.

Warranty

Most online mattress brands offer a warranty of at least 10 years. Most high-quality mattresses last for about 8 to 10 years, so a 10-year warranty guarantees the bed consistently supports you throughout its expected lifespan.

A warranty longer than 10 years is typically prorated. A prorated warranty fully covers repairs and replacements during the first 10 years of use. However, after the first 10 years, the customer is responsible for paying a percentage of the replacement cost.

Sleep Trial

Online mattresses tend to have a lengthier sleep trial period than mattresses purchased from brick and mortar retailers. Online companies understand customers don’t get to try out the bed before buying, so they offer them plenty of time to make sure the bed meets their needs. Plus, a short 10-minute mattress “test” is not enough to determine the comfort of the bed. It takes 2 to 3 weeks to become accustomed to the feel of a new mattress.

As you shop for the best mattress in a box, look for beds with at least a 90-day sleep trial. Sleeping on the bed at home for 3 months gives you a better idea of the comfort and support it may offer. If you are not happy with your choice after trying it out for a while, the brand works with you to exchange it or provide you with a full refund.

Saving on a King Size Mattress

Mattresses in a box have a well-established reputation for their budget-friendly prices. Still, as the largest standard size mattress, a king bed can cost quite a lot. However, you can save considerably by shopping the year’s big mattress sales:

• Presidents Day Mattress Sales
• Memorial Day Mattress Sales
• 4th of July Mattress Sales
• Labor Day Mattress Sales
• Columbus Day Mattress Sales
• Black Friday Mattress Sales
• Cyber Monday Mattress Sales

However, it’s important to remember that the best time to buy a mattress is almost always once you notice it needs replacing. Otherwise, you can lose hours of precious sleep every night.

Frequently Asked Questions

What size bed do most couples have?

Most couples have a queen or a king size mattress. A queen size bed measures 60 inches wide by 80 inches long. These beds are popular with couples because they give each sleeper 30 inches of personal space. However, for couples who need more room to stretch out or families who prefer to co-sleep, a king is a better option. A king size mattress measures 76 inches by 80 inches, giving each sleeper 38 inches of space.

How long do mattress in a boxes last?

The lifespan of a mattress in a box varies depending on the type of materials used for construction. This is true of all beds, including those found at mattresses retailers. A high-quality memory foam mattress lasts 8 to 10 years, while latex foam beds tend to last around 12 years. Depending on the type of foam used in the comfort layer, hybrid mattresses last between 8 and 12 years.

Can you put mattresses directly on slats?

Yes, most modern mattresses can be placed directly on the slatted foundation of your bed frame. However, if your mattress contains foam, these slats should be no more than 3 inches apart to prevent sagging and indentations.

Can I use plywood instead of a box spring?

Some foam mattresses become damaged if they are placed on a box spring. If you do not have a solid foundation, use a 2-inch piece of moisture-resistant plywood to protect the mattress. Plywood can be placed directly on a slatted bed frame or on top of a box spring. However, box springs and plywood should never be used on an adjustable base.

Is there a bed bigger than a king?

King and California king size beds are the biggest standard size mattresses. King mattresses measure 76 inches wide by 80 inches long. California kings are slightly smaller but longer; they measure 72 inches wide by 84 inches long. This extra length makes them perfect for taller individuals.

Although it is often difficult to find mattresses bigger than a king or Cal king, they are available. A Wyoming king mattress measures 84 inches wide by 84 inches long, and Texas king measures 80 inches wide and 98 inches long. The biggest bed size available is an Alaskan king, which measures 108 inches wide by 108 inches long.

Conclusion

If you’re thinking of purchasing a king size mattress, shopping with one of the many mattress in a box brands will make the process easier and more affordable. Plus, with a longer sleep trial and a more transparent warranty, you’ll have the peace of mind knowing your investment is protected. By keeping your needs in mind, you are sure to find a mattress that promotes a better night’s sleep.