A 12-inch gel memory foam king mattress can offer a balance of contouring comfort, pressure relief, and a supportive foam base. But “cooling” means different things across models: some use gel-infused foam, while others also describe open-cell foam or a cool-touch cover. Compare the feel, construction, certifications, and setup details below—and check that the King size is selected before ordering.
Quick Comparison
| Mattress | Feel or standout feature | What to know |
|---|---|---|
| COOL GEL 12-Inch King Mattress | Medium firm; open-cell cooling design | King dimensions are listed as 80 × 76 inches; CertiPUR-US certified |
| Best Price Mattress 12-Inch Memory Foam | Medium firm; gel-infused foam | Confirm the King size option before purchase; listed to expand within 72 hours |
| Novilla Bliss Cooling King Mattress | Cool-touch cover and NanoGEL foam | Listing data indicates it may be unavailable; check the current listing |
| ZINUS Green Tea Cooling Gel Mattress | Gel and green tea infused foam | Confirm the King size option; allow 24–72 hours for expansion |
| LUCID 12-Inch Gel Memory Foam Mattress | Medium plush; gel foam and bamboo charcoal | King size; compatible with adjustable, platform, and slatted frames |
Our Picks: Best 12 Inch Cool Gel Memory Foam Mattress King reviews
1. COOL GEL 12-Inch King Mattress: Medium-Firm Support
This model is a straightforward choice if you want a King mattress with a stated medium-firm feel. Its construction combines a breathable comfort foam layer with a high-density foam base. The brand says the foam adapts to the body and spreads weight to ease pressure points.
Its open-cell design is intended to encourage airflow and heat dissipation. That may appeal if you want a foam mattress with cooling features, though foam can still feel warmer to some sleepers than a more breathable mattress type. The product is listed as 80 by 76 inches and 12 inches deep.
The mattress is described as made in the USA with CertiPUR-US certified materials and as fiberglass-free. Its medium-firm feel is positioned for back, side, and stomach sleepers, but comfort is personal: side sleepers who prefer a softer surface may want a more cushioning option, such as the plush LUCID.
Pros:
- King dimensions and 12-inch profile are clearly specified.
- Medium-firm feel aims to balance cushioning and support.
- Open-cell foam design is intended to improve airflow.
- Listing states that it is fiberglass-free and CertiPUR-US certified.
Cons:
- Medium firm may not feel plush enough for sleepers who want a deeper sink-in feel.
- Cooling features do not guarantee that every sleeper will stay cool.
Verdict: Choose the COOL GEL if you want a clearly specified King size, medium-firm support, and an open-cell foam design.
2. Best Price Mattress: Gel-Infused Medium-Firm Foam
The Best Price Mattress pairs gel-infused memory foam with a medium-firm feel. The product description says the foam conforms to the body and is designed to ease pressure, while its breathable construction aims to support airflow. It is a simpler feature set than models that list a special cover or more detailed foam layers.
The mattress ships compressed, which can make it easier to move into a bedroom than a fully expanded mattress. The listing says it can take up to 72 hours to expand to its full size. Since the provided product title and description do not specify King dimensions, check that the King size is available and selected on the listing before buying.
This may suit shoppers looking for a medium-firm gel foam option without needing a long list of extras. The trade-off is that the supplied details do not name a specific foam certification, warranty, or King measurements, so verify those details if they matter to your decision.
Pros:
- Gel-infused memory foam is designed to contour and relieve pressure.
- Medium-firm feel offers a middle ground between soft and firm.
- Breathable design is intended to help maintain airflow.
- Compressed packaging can simplify delivery and setup.
Cons:
- King dimensions are not included in the supplied product details.
- Expansion may take up to 72 hours.
Verdict: Consider this model if its listing confirms the King size and you want a basic medium-firm gel foam mattress with convenient boxed delivery.
3. Novilla Bliss: Cool-Touch Cover and Layered Support
The Novilla Bliss stands out for its combination of a cool-touch nylon cover and NanoGEL memory foam. The cover is described as blended with plant-infused fiber, while the foam is designed to promote airflow. These features give it a more cover-focused cooling approach than the other picks, which mainly highlight gel or open-cell foam.
Inside, the mattress uses three foam layers: gel foam, cushioning foam, and high-density support foam. The design is intended to cushion pressure points while limiting excessive sink. The listing also describes motion isolation and reinforced edges, which may be useful if you share a bed or use more of the mattress surface.
The product description lists CertiPUR-US foam, OEKO-TEX certified fabric, a 10-year protection period, and a 100-night trial. Confirm the terms on the product page. The supplied availability information indicates that this mattress may currently be unavailable, so check the listing before making it your first choice.
Pros:
- Cool-touch cover adds a cooling feature beyond gel-infused foam.
- Three-layer design combines cushioning with a high-density support layer.
- Listing describes reinforced edges and motion isolation.
- King size and 12-inch height are specified in the product title.
Cons:
- The supplied listing data indicates that it may be unavailable.
- Trial and protection terms should be checked before ordering.
Verdict: If it is available, the Novilla is worth considering if you want a cool-touch cover and layered foam design; confirm current availability and terms first.
4. ZINUS Green Tea Cooling Gel: Layered Foam Construction
The ZINUS combines cooling gel and green tea infused memory foam in a three-part construction. The listed layers include 2 inches of infused memory foam, 3 inches of comfort foam, and a 7-inch high-density base. This makes its construction more specific than some of the other options in this roundup.
The product description calls out pressure relief and says the design may suit side sleepers and average-weight sleepers. It also lists CertiPUR-US certified foam and a 10-year limited warranty. The description mentions a maximum weight of 500 pounds for sizes other than Twin; check the current listing for the exact size and terms you need.
Like other boxed foam mattresses, this one needs time to regain its shape. The maker advises allowing 24 to 72 hours, with expansion affected by room temperature. The supplied title does not specify King, so confirm the King option is selected before placing an order.
Pros:
- Specific foam-layer breakdown makes the construction easy to compare.
- Gel and green tea infused memory foam is designed for cooling and pressure relief.
- CertiPUR-US certification and a 10-year limited warranty are listed.
- Product details provide a maximum weight for sizes other than Twin.
Cons:
- King availability should be confirmed on the product page.
- It may need up to 72 hours to fully expand.
Verdict: The ZINUS is a good fit if you value a clearly described foam-layer setup, provided the King size is offered in the listing.
5. LUCID 12-Inch Gel Memory Foam: Medium-Plush Comfort
The LUCID is the plushest-feeling choice in this group. Its medium-plush feel and 3.5 inches of comfort foam are designed to contour around the body, with extra cushioning around areas such as the hips and shoulders. That can appeal to side sleepers who prefer a softer surface, though it may feel less supportive to sleepers who want a firmer mattress.
Its three layers include 3 inches of gel memory foam, a 1.5-inch transition layer, and a 7.5-inch high-density base. The description also notes bamboo charcoal, which is intended to absorb moisture and help regulate temperature. The King size is specified, and the mattress is listed as compatible with adjustable bases, platform frames, and slatted frames.
The foam is CertiPUR-US certified, and the product includes a 10-year limited warranty. LUCID is the most clearly described option here for shoppers who want a softer feel and flexible frame compatibility, rather than a medium-firm surface.
Pros:
- Medium-plush feel offers more cushioning than the medium-firm picks.
- Layered construction includes gel foam, a transition layer, and a dense base.
- Compatible with adjustable, platform, and slatted frames.
- King size, CertiPUR-US certification, and a 10-year limited warranty are listed.
Cons:
- May feel too soft for people who prefer medium-firm support.
- Its plush contouring may not suit everyone who sleeps on their stomach.
Verdict: Choose the LUCID if you want a King mattress with a medium-plush feel, deeper cushioning, and support for several frame types.
How to Choose a 12-Inch Cool Gel Memory Foam King Mattress
Confirm the size before you buy
A 12-inch profile describes mattress thickness, not its width or length. Check that the product page shows a King option and review the dimensions before ordering. This is especially important for models whose supplied descriptions do not name a King size directly. The COOL GEL listing specifies dimensions of 80 by 76 inches.
Choose a feel that matches how you sleep
Medium-firm and medium-plush mattresses can feel quite different. A medium-firm option may suit you if you want a more balanced, supportive surface. A medium-plush mattress such as the LUCID offers more cushioning and contouring, which may appeal to side sleepers who like a softer feel. Your preferred firmness is personal, so consider what feels comfortable to you rather than relying on labels alone.
Look beyond the word “cooling”
Gel infusion is common in this group, but the designs vary. The COOL GEL highlights open-cell foam, the Novilla adds a cool-touch cover, and LUCID combines gel foam with bamboo charcoal. These features are intended to help manage heat or airflow, but they do not guarantee a cool feel for every person. If you tend to sleep warm, compare the full construction rather than choosing by the word “gel” alone.
Compare the foam layers and support base
Memory foam provides contouring, while a denser base layer supports the mattress structure. Some listings give a detailed layer breakdown, such as ZINUS and LUCID, while others describe the materials more generally. A fuller description makes it easier to compare the cushioning layer with the support beneath it and decide whether the design suits your comfort preferences.
Check certifications, warranty, and trial terms
Certifications and policies differ across these products. Several listings specify CertiPUR-US certified foam, and the Novilla description also names OEKO-TEX certified fabric. Warranty and trial details are not identical, so read the current product page carefully for the coverage, limits, and any conditions that apply.
Plan for boxed-mattress setup
Some models ship compressed and need time to expand after unboxing. The Best Price Mattress listing says to allow up to 72 hours, while ZINUS gives a 24-to-72-hour window. Keep the mattress in a suitable room while it expands, and follow the maker’s setup and care directions. If you need a specific frame, check compatibility before ordering; LUCID lists adjustable, platform, and slatted frames as compatible.
Frequently Asked Questions
Is a 12-inch mattress thick enough for a King bed?
Thickness and size are separate measurements. A 12-inch mattress can be offered in King size, but check the listing’s size selection and dimensions to make sure you are ordering the right fit for your bed frame.
Does gel memory foam guarantee a cooler night’s sleep?
No. Gel, open-cell foam, and cool-touch covers are designed to help with temperature regulation, but individual comfort varies. Consider the mattress’s full construction and your own preferences.
Which mattress here has the firmest feel?
The COOL GEL, Best Price Mattress, and ZINUS options are described as medium firm or use a medium-firm design. Firmness can feel different from person to person, so the label is best used as a general guide.
Which option is the plushest?
The LUCID is described as medium plush and has a comfort layer designed to contour around the body. It may be a better match if you prefer more cushioning than the medium-firm options provide.
How long should a boxed mattress take to expand?
It depends on the model. The supplied Best Price Mattress details say up to 72 hours, while ZINUS advises allowing 24 to 72 hours. Follow the instructions for the mattress you choose, since room temperature can affect expansion.
Can I use these mattresses on an adjustable base?
The LUCID listing specifically says it is compatible with adjustable bases, as well as platform and slatted frames. For the other models, check the product page or contact the manufacturer to confirm compatibility with your base.
Final Recommendation
For a clearly specified King size and medium-firm feel, the COOL GEL 12-Inch King Mattress is the most straightforward pick in this group. Choose the LUCID if you want a softer, more contouring feel, or consider the ZINUS for its detailed foam-layer construction after confirming King availability. Whichever one you choose, verify the size, setup instructions, and current terms on the product listing before ordering.