9 Best Extra Firm Mattress King (November 2026)

The best extra firm king mattresses include the Zinus Memory Foam 12 Inch Green Tea for softer memory foam support, the Signature Design by Ashley 12 Inch Hybrid for coil-and-foam balance, and the EGOHOME King Size Memory Foam Mattress for cooling memory foam.

On this page (3 sections)

1. The best extra firm king mattresses for different sleepers
2. How to choose an extra firm king mattress
3. Which extra firm king mattress should you buy?

The best extra firm mattress king for most shoppers is the Sleepmax Extra Firm King Mattress because it is clearly labeled extra firm, with a 14-inch hybrid build and reinforced edge support. That makes it the easiest starting point if you want a hard, stable surface rather than a soft foam cradle.

VISCOFLEX is the better pick for a 12-inch profile, while FP FLEXPEDIC suits shoppers who prefer firm rather than extra firm. Those choices cover the main firmness range here without forcing you into a medium or plush bed.

Height affects fit, not just comfort. A 12-inch mattress usually suits an existing frame and sheets, while 14-inch or 16-inch models raise the bed and may change how a fitted sheet sits.

Construction matters as much as the label. Hybrids pair foam with individually pocketed coils for a firmer, more responsive feel, while all-foam models let the body settle in more deeply.

Several softer options are included because labels vary by brand. Zinus, Ashley, EGOHOME, Novilla Bliss, Grbsy and Novilla are medium, medium firm or medium plush, so they work as alternatives when extra firm feels too hard.

Softer options can also help couples split the difference. One partner may want a very firm surface, while the other needs more give at the shoulder and hip.

Sleep position and body weight should shape your shortlist. Back sleepers often tolerate a firmer top layer better, while side sleepers usually need more cushioning, and lighter sleepers may feel an extra firm coil layer more strongly.

Most of these mattresses arrive compressed, so unbox in the right room and allow full expansion before judging the feel. A flat, supportive base and reinforced edges also help a king mattress stay even and feel steadier at the perimeter.

CertiPUR-US certified foam and fiberglass-free designs appear in several models, which may matter if you prefer a cleaner material profile.

For a softer king-size comparison, see plush king mattresses.

If you're still deciding how firm your bed should feel, read our guide to the best extra firm mattress and learn whether a mattress should be firm.

Our picks at a glance

1. 1
   Best for softer memory foam support

   Zinus Memory Foam 12 Inch Green Tea

   9.7/10 our score

   See it on Amazon
2. 2
   Best for coil-and-foam balance

   Signature Design by Ashley 12 Inch Hybrid

   9.7/10 our score

   See it on Amazon
3. 3
   Best for cooling memory foam

   EGOHOME King Size Memory Foam Mattress

   9.6/10 our score

   See it on Amazon

4. 4

   Novilla Bliss Mattress King Size

   Best for plush pressure relief
   Check it
5. 5

   FP FLEXPEDIC Firm King Mattress 12 Inch

   Best for zoned firm support
   Check it
6. 6

   Grbsy 16 Inch King Size Mattress

   Best for tall hybrid cushioning
   Check it
7. 7

   Sleepmax Extra Firm King Mattress 14 Inch

   Best for a clearly extra firm feel
   Check it
8. 8

   VISCOFLEX Extra Firm King Mattress 12 inch

   Best for a lower extra firm profile
   Check it
9. 9

   Novilla 12 Inch King Size Mattress

   Best for a softer hybrid alternative
   Check it

The best extra firm king mattresses for different sleepers

Sleepmax and VISCOFLEX are the closest matches for a distinctly extra firm surface. FP FLEXPEDIC gives you a firm hybrid feel, while the remaining mattresses offer more support with softer cushioning.

That split is the main theme here. Only two models are labeled extra firm and one is labeled firm, with the rest medium, medium firm or medium plush.

Firmness labels are not standardized across brands. One brand may call a surface firm while another uses the same word for a noticeably harder feel, so treat the label as a guide rather than a guarantee.

Construction and height help explain the differences. Coils add bounce and structure, thick memory foam adds contouring, and taller models often have a plusher top that can soften a firm coil base.

Our score weighs specs, features and buyer feedback against the needs of an extra firm king shopper. Labeled firmness and hybrid build therefore matter more than extra comfort features, though a high score does not always mean the firmest feel.

Use the rankings as a starting point, then read each write-up for the trade-offs. The right choice depends on whether you want maximum firmness, a lower profile, zoned support or more cushioning.

1

Zinus Memory Foam 12 Inch Green Tea: Best for softer memory foam support

9.7/10Our score

• 12-inch memory foam construction
• 3 inches of conforming memory foam
• King size, 80 x 76 x 12 inches
• Up to 500 lb support for non-twin sizes

Zinus suits shoppers who want pressure-relieving memory foam rather than a distinctly extra firm surface. Green tea and ActivCharcoal are infused into the foam, and the mattress arrives compressed in a box.

See it on Amazon

Pros

• 12-inch profile
• CertiPUR-US certified foam
• 10-year limited warranty

Cons

• Medium firm, not extra firm
• Memory foam feel may allow more sink

Zinus is the softest match among the top-scoring options here. Its 12-inch memory foam build has 3 inches of conforming memory foam, 2 inches of airflow-enhancing comfort foam and 7 inches of high-density base support foam.

The top foam can cradle shoulders and hips, the middle layer adds softness and airflow, and the thick base helps prevent a flat feel. Zinus describes the result as medium firm, so expect cradling rather than the harder surface of an extra firm bed.

The king mattress measures 80 x 76 x 12 inches and supports up to 500 lb for non-twin sizes. That capacity does not mean it will feel extra firm at that weight.

Green tea and ActivCharcoal are infused into the memory foam to keep it feeling fresher, and the foam is CertiPUR-US certified. Zinus includes a 10-year limited warranty and lists spot cleaning as the care method.

The mattress arrives compressed, so allow 24 to 72 hours for full expansion, with warmer rooms helping recovery. Choose it for pressure-relieving memory foam support, or move to Sleepmax or VISCOFLEX for a distinctly extra firm surface.

2

Signature Design by Ashley 12 Inch Hybrid: Best for coil-and-foam balance

9.7/10Our score

• 12-inch hybrid construction
• 360 individually wrapped coils
• Two perimeter rows
• King size, 76 x 79.5 x 12 inches

This Ashley hybrid is a better fit for shoppers who want coils, foam and reduced motion transfer but do not require an extra firm feel. The foundation, box spring and frame are sold separately.

See it on Amazon

Pros

• 360 wrapped coils
• Two perimeter rows
• Medium firm comfort layers

Cons

• Medium feel
• Foundation sold separately

The Ashley hybrid suits buyers who want 360 individually wrapped coils and foam layers rather than an all-foam mattress. Two perimeter rows add edge structure, while the pocketed coil design is intended to reduce motion transfer.

Individually wrapped coils respond one by one rather than as a single connected unit. For couples, that can mean less disturbance when one person shifts position during the night.

This king mattress is 12 inches tall and measures 76 x 79.5 inches. The slightly different length compared with other king models here is worth checking against your frame before you order.

Its construction includes gel memory foam, upholstery-grade support foam and quilt foam. Those layers are meant to add surface comfort over the coil base, with extra attention to lumbar support.

The feel is medium, so it does not belong in the extra firm group by feel. Shoppers who want a hard, flat surface will likely notice the cushioning from the foam and quilt layers fairly quickly.

The mattress arrives compressed in a box. Ashley says to allow 48 hours for full expansion, so it is wise to unbox it early in the day and avoid judging the firmness on the first evening.

A bed foundation, box spring or frame is sold separately, so plan the base before delivery. A sturdy, even base will help the coils support the full king width without creating weak spots.

Care is mostly about protecting the cover and keeping the base clean and dry. A fitted sheet and mattress protector can reduce wear on the surface and make routine laundering easier.

Pick Ashley when coil support and a medium surface feel matter more than maximum firmness. For a firmer hybrid, FP FLEXPEDIC is the closer step.

3

EGOHOME King Size Memory Foam Mattress: Best for cooling memory foam

9.6/10Our score

• 12-inch king memory foam mattress
• Green tea gel memory foam
• Medium firm feel
• 80 x 76 x 12 inches

EGOHOME fits buyers who want a 12-inch medium firm memory foam mattress with green tea gel and breathable foam structure. It is not an extra firm model, but it offers a useful softer alternative.

See it on Amazon

Pros

• Cooling green tea gel
• CertiPUR-US certified
• 10-year warranty

Cons

• Medium firm rather than extra firm
• All-foam feel

EGOHOME is a 12-inch medium firm memory foam mattress with a king footprint of 80 x 76 inches. Its green tea gel memory foam and bubble-hole structure are aimed at pressure relief and airflow.

The foam is designed to adapt as you change positions, which can appeal to combination sleepers who do not want a rigid surface. The trade-off is clear: medium firm does not provide the same feel as an extra firm mattress.

EGOHOME states that its foam is CertiPUR-US certified and that the mattress is fiberglass free. It also includes a 10-year warranty.

Give a compressed mattress time to expand before deciding whether the feel suits you.

This is a useful alternative if extra firm sounds uncomfortable but you still want stable memory foam support. Compare it with what a medium firm mattress feels like before choosing.

4

Novilla Bliss Mattress King Size: Best for plush pressure relief

9.5/10Our score

• 14-inch memory foam construction
• NanoGel memory foam
• Medium plush feel
• Reinforced edge support

Novilla Bliss is the softest-feeling option in this comparison, with a 14-inch, 3-layer foam design and gel memory foam. Choose it when pressure relief matters more than an extra firm surface.

See it on Amazon

Pros

• 14-inch profile
• Motion isolation
• 100-day trial and 10-year protection

Cons

• Medium plush feel
• May feel too soft for extra firm shoppers

Novilla Bliss is the plushest option in this comparison. Its 14-inch, 3-layer memory foam design uses NanoGel memory foam, comfort foam and support foam, with a soft knitted cover.

The extra height gives the foam more room to contour around the body. That can help pressure relief at the shoulders, hips and knees, and may suit combination sleepers who move between back and side positions.

The king mattress measures 80 x 76 x 14 inches and is described as medium plush. It is therefore better for shoppers who want cushioning than for people who want an extra firm surface.

Reinforced edge support helps create a steadier perimeter, and the foam is CertiPUR-US certified. Gel memory foam and a breathable knit cover are intended to help with cooling, though an all-foam bed still feels different from a coil hybrid.

The mattress arrives compressed and may take up to 72 hours to regain its full shape. Novilla lists a 100-day trial and 10-year protection plan, which can help if you are unsure whether a plush surface will suit you.

Choose Bliss when you want the most cushioning here. If you are comparing all available sizes, our best extra firm mattress full and best extra firm mattress queen guides cover smaller footprints.

5

FP FLEXPEDIC Firm King Mattress 12 Inch: Best for zoned firm support

9.3/10Our score

• 12-inch firm hybrid
• Zoned foam and spiral coils
• Reinforced perimeter coils
• Supports up to 1000 lb

FP FLEXPEDIC is a strong choice for shoppers who want a firm king hybrid with zoned support and reinforced edges. Its firm feel is closer to the target than the medium and plush models, though it is not labeled extra firm.

See it on Amazon

Pros

• Firm feel
• Zoned lumbar, hip and shoulder support
• 365-night trial

Cons

• Firm rather than extra firm
• Heavier 105 lb mattress

FP FLEXPEDIC is the best middle ground for shoppers who want a firm king hybrid but are not sure an extra firm surface will feel comfortable. Its 12-inch design combines individually wrapped pocket springs, zoned foam and gel-infused foam.

Zoning is the key idea here. Instead of treating the whole surface the same way, the design aims to give different support under different parts of the body.

The zoned design places softer cushioning at the shoulders and hips while adding lumbar support. That can help back sleepers keep a more neutral spine while still giving side sleepers some give where they need it.

Reinforced perimeter coils help reduce roll-off, and FP FLEXPEDIC states that the mattress supports up to 1000 lb. A higher capacity can be helpful for larger sleepers or couples who share the bed.

This model is labeled firm, not extra firm. That distinction matters because the foam and Euro top add cushioning that can soften the coil response compared with a mattress labeled extra firm.

It is also one of the heavier mattresses here at 105 lb, so plan the route to the bedroom before unboxing. A second person can make setup safer, especially when moving a king mattress through hallways and doorways.

The mattress includes a user manual and lifetime warranty card. Keeping the card and manual in an easy place can make warranty or care questions simpler later.

FP FLEXPEDIC also describes the mattress as fiberglass free. That may be a priority for households that prefer to avoid fiberglass in bedding materials.

Choose it for a firm, supportive hybrid with targeted zones. For the hardest labeled feel in this roundup, select Sleepmax or VISCOFLEX.

6

Grbsy 16 Inch King Size Mattress: Best for tall hybrid cushioning

9.2/10Our score

• 16-inch hybrid construction
• 7-zone ergonomic support
• 1000 pocket springs
• King size, 80 x 76 x 16 inches

Grbsy gives you the tallest profile here, with a Euro-top, gel memory foam and 7-zone support. Its medium firm feel adds cushioning, so it suits buyers who want hybrid support without a hard extra firm surface.

See it on Amazon

Pros

• 16-inch profile
• 7-zone support
• 365-night trial

Cons

• Medium firm, not extra firm
• Tall profile may need fitted-sheet planning

Grbsy is the tallest mattress here at 16 inches, with a Euro-top, gel memory foam and a pocketed spring base. Its 7-zone design aims to support the shoulders, hips and lower back while keeping the surface cushioned.

The king mattress measures 80 x 76 x 16 inches and uses 1000 pocket springs. Individually pocketed springs can help limit motion transfer, which is useful if you share the bed with a restless partner.

Grbsy describes the feel as medium firm, so the extra height adds cushioning rather than creating an extra firm mattress. The hybrid design includes airflow spaces between coils, a cooling cover and reinforced edges.

Grbsy states that the mattress is fiberglass free and backed by a 365-night trial. A long trial can be helpful when you are unsure how a tall, cushioned hybrid will feel over time.

The trade-off is practical. You may need deeper sheets, a frame that can handle the height and enough clearance around the bed.

At 105 lb, it is also heavy to move, so unbox in the final room and allow full expansion before making the bed.

7

Sleepmax Extra Firm King Mattress 14 Inch: Best for a clearly extra firm feel

9.2/10Our score

• 14-inch extra firm hybrid
• Pocketed coils and gel memory foam
• Reinforced edge support
• Box spring, slatted base and solid foundation compatibility

Sleepmax is the clearest match for this roundup because its firmness is labeled extra firm. Its 14-inch hybrid design combines pocketed coils, gel memory foam and reinforced edges for a firm, stable sleep surface.

See it on Amazon

Pros

• Extra firm feel
• 365-night trial
• Fiberglass-free materials

Cons

• 104 lb mattress
• May feel too hard for side sleepers who prefer more cushioning

Sleepmax is the best direct match for an extra firm king mattress. It is labeled extra firm and combines a 14-inch hybrid structure with pocketed coils, gel memory foam, a deluxe Euro top and reinforced edge support.

That label is the main reason it leads this roundup. If medium firm is already too soft for you, starting with a model actually labeled extra firm removes guesswork.

The hybrid construction is designed to spread body weight and limit motion transfer. Sleepmax says it suits back, side and combination sleepers, but side sleepers who need deep shoulder cushioning may still prefer a less firm surface.

For back sleepers, the coil base can feel supportive because it resists sinking. For side sleepers, the foam layers need to do more work to cushion the shoulder and hip.

The king mattress measures 80 x 76 x 14 inches and works with a box spring, slatted base or solid foundation. Sleepmax identifies the materials as CertiPUR-US and OEKO-TEX certified and fiberglass free.

Reinforced edges help the mattress feel steadier near the perimeter. At 104 lb, it is heavy to move, so plan the route to the bedroom and use help during setup.

8

VISCOFLEX Extra Firm King Mattress 12 inch: Best for a lower extra firm profile

9.1/10Our score

• 12-inch extra firm hybrid
• Gel memory foam and pocketed coils
• Extra lumbar and hip support
• 365-night trial and 10-year warranty

VISCOFLEX is a practical pick when you want an extra firm king mattress without the taller 14- or 16-inch profile. Its hybrid design uses gel memory foam and pocketed coils with extra lumbar and hip support.

See it on Amazon

Pros

• Extra firm feel
• 12-inch height
• Fiberglass-free materials

Cons

• Heavier 114 lb mattress
• Less cushioning than taller models

VISCOFLEX gives you an extra firm feel in a 12-inch king hybrid. It combines gel memory foam with pocketed coils and adds extra lumbar and hip support for shoppers who want a lower profile than the 14-inch Sleepmax.

The mattress measures 80 x 76 x 12 inches and arrives in a box. VISCOFLEX describes its pocketed coil system as breathable and motion isolating, while the foam layer adds some cushioning over the springs.

It is labeled fiberglass free and uses CertiPUR-US and OEKO-TEX certified materials. VISCOFLEX includes a 365-night home trial and 10 years of coverage.

At 114 lb, it is the heaviest mattress in this group, so use care during setup.

Pick VISCOFLEX when you want extra firm support without a 14-inch or 16-inch mattress. Its profile also makes it a useful comparison with our best extra firm mattress twin guide if you are furnishing more than one room.

9

Novilla 12 Inch King Size Mattress: Best for a softer hybrid alternative

8.9/10Our score

• 12-inch hybrid construction
• SmartS coils and contouring foam
• Reinforced perimeter support
• AirBreeze fabric

This Novilla gives extra firm shoppers a softer hybrid alternative with AirBreeze fabric, SmartS coils and reinforced edges. Its medium plush feel makes it better for buyers who want support with more surface cushioning.

See it on Amazon

Pros

• 12-inch profile
• Fiberglass-free
• Reinforced edges

Cons

• Medium plush feel
• Not designed as an extra firm mattress

Novilla's 12-inch hybrid is a softer alternative to the two extra firm picks. Its medium plush feel combines SmartS coils, contouring foam, AirBreeze fabric and reinforced perimeter support.

That mix gives you coil structure without the hard surface of an extra firm mattress. The foam can cradle pressure points while the springs add a level of response that all-foam beds do not have.

The king mattress measures 80 x 76 x 12 inches. The hybrid design gives you coil response and edge stability, while the foam is intended to cradle pressure points for side, back and stomach sleepers.

For side sleepers, the contouring foam may be the most noticeable part of the feel. It can help the shoulder and hip settle into the surface instead of resting on top of a very firm layer.

Novilla identifies the mattress as fiberglass free, with CertiPUR-US foam and an OEKO-TEX cover. Those material details can be useful if you are comparing a hybrid against all-foam models on safety and certification.

It arrives in a box, so give it time to expand before evaluating its final shape. Rushing that step can make the surface feel uneven and can lead to a poor first judgment.

Reinforced perimeter support is also worth noting for a king size. A steadier edge can make sitting up in bed or getting dressed feel safer and can help the full width feel more usable.

At 66 lb, it is lighter than several other king models here. That can make moving it into the bedroom easier, although four hands are still a smart choice for a king mattress.

Choose this mattress if you want a 12-inch hybrid with more surface cushioning. It is not the right pick if your main goal is the firmest feel available.

How to choose an extra firm king mattress

The best extra firm mattress king choice depends first on the firmness label, then on the construction and height. Start with Sleepmax or VISCOFLEX if you want an explicitly extra firm surface.

Extra firm versus firm

Sleepmax and VISCOFLEX are labeled extra firm. FP FLEXPEDIC is labeled firm, which may feel more forgiving because its zoned foam and Euro top add cushioning over the coils.

Labels are not a complete comfort test. Your body weight, sleep position and preferred pressure relief can make the same mattress feel different, so use the trial terms where available.

Foam versus hybrid construction

Memory foam gives you more contouring and less spring response. Zinus and EGOHOME are medium firm, while Novilla Bliss is medium plush, so these are better alternatives if extra firm feels too hard.

Hybrid mattresses combine foam with coils. Sleepmax and VISCOFLEX are the direct extra firm choices, while FP FLEXPEDIC, Ashley, Grbsy and Novilla offer progressively softer firm or medium feels.

Mattress height and bedroom setup

A king mattress is commonly about 76 x 80 inches, but exact dimensions vary. Ashley measures 76 x 79.5 inches, while the other king models here generally measure 80 x 76 inches.

That half-inch difference can matter for sheets and frames. Measuring your frame before ordering is the safest way to avoid a loose or tight fit.

Height also changes how high your bed sits. The 12-inch models are easier to pair with an existing frame, while 14-inch and 16-inch mattresses need fitted sheets with enough pocket depth.

A taller mattress can change the feel too. More height often means more foam and a plusher top layer, which can soften the firmness you might expect from a coil base.

Frame height and mattress height work together in daily use. A high frame plus a 16-inch mattress can make getting into bed less convenient, especially for shorter sleepers.

If a fitted sheet lacks pocket depth, the corners can pull loose and the surface can feel wrinkled. Heavier king mattresses can also be harder to move through tight hallways, so plan the route before the box arrives.

Check base compatibility before delivery rather than after unboxing. A compatible foundation helps support weight evenly and can affect how firm the surface feels.

Expansion time belongs in your setup plan as well. Most of these mattresses arrive compressed and need time to regain their shape before you judge firmness or make the bed.

Edge support and motion transfer

Reinforced edges can make it easier to sit near the perimeter and use more of the surface. Sleepmax, VISCOFLEX, Grbsy and Novilla include edge-support features, while Ashley uses two perimeter rows.

Pocketed coils can also reduce movement transfer compared with a connected coil design. If you share the bed, look for a hybrid that combines independent coils with foam rather than choosing firmness alone.

Expansion and care

Most of these mattresses arrive compressed in a box. Move the box close to the final room, remove the packaging on a clean surface and let the mattress expand before judging its firmness.

Zinus advises 24 to 72 hours for full shape recovery. Ashley advises 48 hours.

Spot-clean the Zinus mattress only, and follow each brand's care directions for the other models.

Which extra firm king mattress should you buy?

Choose Sleepmax if you want the clearest extra firm feel with a 14-inch hybrid build and flexible foundation compatibility. Choose VISCOFLEX if you want the same labeled firmness in a 12-inch profile.

If height is your main concern, that profile difference can decide the pick. A 12-inch mattress is usually easier to fit with existing sheets and a lower frame, while a 14-inch model gives you a taller hybrid build.

Pick FP FLEXPEDIC if firm is enough and you want zoned support. Its firm label and targeted lumbar, hip and shoulder support make it a step down from extra firm without moving all the way to medium firm.

Choose Zinus, Ashley, EGOHOME, Grbsy or Novilla when you prefer medium, medium firm or plush cushioning over a hard extra firm surface. Those models can still offer strong support, but the surface will feel softer under the shoulders and hips.

Before you order, match the mattress to your sleep position. Back sleepers often do well with firmer hybrids, while side sleepers may need more foam cushioning even if they like a supportive base.

Also check the base and sheets before delivery. A compatible foundation helps any king mattress feel even, and taller models need fitted sheets with enough pocket depth to stay secure.

Give the mattress time to expand before you decide whether the feel is right. Compressed foam and coils need their full recovery window, and judging firmness too early can lead to the wrong conclusion.

If you are unsure whether your current preference is firm enough, compare the guidance in Best Firm King Size Pillow Top Mattresses before ordering.

Our top 3 picks at a glance

1. 1
   Best for softer memory foam support

   Zinus Memory Foam 12 Inch Green Tea

   9.7/10 our score

   See it on Amazon
2. 2
   Best for coil-and-foam balance

   Signature Design by Ashley 12 Inch Hybrid

   9.7/10 our score

   See it on Amazon
3. 3
   Best for cooling memory foam

   EGOHOME King Size Memory Foam Mattress

   9.6/10 our score

   See it on Amazon

Frequently asked questions

What is the best extra firm mattress king?

The Sleepmax Extra Firm King Mattress is the strongest overall match because it is labeled extra firm and combines a 14-inch hybrid profile with pocketed coils, gel memory foam and reinforced edge support.

Choose VISCOFLEX if you want a 12-inch extra firm profile. FP FLEXPEDIC is a good alternative if firm is enough.

Is a firm mattress the same as an extra firm mattress?

No. Firm and extra firm describe different surface feels.

FP FLEXPEDIC is labeled firm, while Sleepmax and VISCOFLEX are labeled extra firm.

Those labels are useful for narrowing your choices, but your body position, weight distribution and preferred cushioning still affect how the mattress feels.

Are extra firm mattresses good for side sleepers?

Extra firm mattresses can feel too hard for some side sleepers because the shoulders and hips may need more cushioning. Sleepmax and VISCOFLEX include foam layers, but a firm or medium firm option may feel more comfortable if you need deeper pressure relief.

Ongoing pain should be discussed with a qualified health professional.

What should go under an extra firm king mattress?

Use a foundation that matches the mattress instructions and provides even support across the king surface. Sleepmax lists compatibility with a box spring, slatted base and solid foundation.

For other models, check the required base type before setup and measure the frame for a 76 x 80 inch king mattress.

How long should a bed-in-a-box mattress expand?

Allow the mattress to regain its shape before judging its feel. Zinus says its compressed mattress may need 24 to 72 hours, while Ashley advises allowing 48 hours for full expansion.

Keep the room warm when possible, remove the packaging carefully and follow the brand's setup instructions.