Yes, you can get a king mattress for under $400 this 4th of July — here’s how – 1v1 Video Chat & LIve Streaming & Influencer Subscription

By Jo Plumridge

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Yes, you can get a king mattress for under $400 this 4th of July — here’s how

Jo Plumridge

4 July 2025

The Serta 10″ Cooling Gel Memory Foam mattress is reduced to $399 at Walmart in today’s sales

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(Image credit: Serta)

A big king size mattress is a joy for couples, giving them plenty of room to spread out. But all that space normally comes with a premium price tag. Not today though — if you’re quick, you can grab a king size 10″ Serta Cooling Gel Memory Foam mattress for only $399 in Walmart’s 4th of July sales. That’s a saving of $400 and an astonishingly good price for a larger size mattress.

Like the best mattresses on the market, the Serta is designed to keep sleepers cool and comfortable at night, with gel infused memory foam and a breathable cover. And, at $399 it could be a perfect pick for guest rooms and college dorms alike.
Walmart has some of the top beds we’d buy in the 4th of July sales this year, so if you’re looking for a bargain king size mattress, make sure you don’t miss out on this offer. Also, check out the latest 4th of July mattress sales that we’re tracking live to find the perfect option for you.

Serta 10″ Cooling Gel Memory Foam mattress: king size $799 $399 at Walmart
If you’re a fan of memory foam but are on a tighter budget, the Serta mattress could be a great choice. At 10″ high it rivals many of the best memory foam mattresses. Sleepers should get plenty of cradling contouring from the gel memory foam, which should also help to keep them cool overnight. Medium firmness means this mattress should appeal to both side and back sleepers, although it’s unlikely to be supportive enough for stomach sleepers. At $399 down from its MSRP of $799 for a king size, it’s a bargain plus you’ll get free shipping and a 90-day return policy.
User score: ★★★★★ (8960+ reviews)

Ideal for guest rooms and college dorms
At $399 for a king size, the Serta Cooling Gel Memory Foam mattress could be a great fit for guest rooms. Like the best mattresses in a box, the Serta comes rolled and in a box, making it easy to deliver just about anywhere.

Guests are sure to appreciate the generous dimensions of a king size mattress and, of course, it could also be a great option as a main bed for those on a budget looking for one of the best cheap mattresses to sleep on.
With an all-foam design, expect the Serta to offer plenty of contouring around pressure points, making it a good choice for those who experience aches, pains and general niggles. It’s also been designed with gel memory foam and a breathable cover to help alleviate overheating issues but really hot sleepers will probably be more comfortable on one of the best cooling mattresses.
Serta offers are fairly frequent but a reduction of $400 to bring a king size mattress down to $399 is a fantastic price.
Looking for a little more back support? Try this instead…

Layla Essential Mattress: king size $799 $649 at Layla
If you’re looking for a cheaper mattress with good back support, the Layla Essential is a great choice. Currently reduced to $649 for a king size, we have previously seen this reduced to $499, but this is still a great price for a mattress that, in our Layla Essential mattress review, we found supportive for back sleepers with decent temperature regulation. You’ll also get free shipping, a 120-night trial and a 10-year warranty.

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Jo Plumridge

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Mattress tester and sleep writer

Jo Plumridge is an experienced mattress reviewer with several years’ experience covering all things mattresses and sleep, and who tests memory foam, hybrid and organic mattresses. What Jo doesn’t know about a boxed mattress isn’t worth knowing, so naturally we tasked her with producing a series of features for Tom’s Guide looking at all aspects of mattresses, from how to pick between latex and memory foam (it’s a tricky one), to the seven mistakes people make when buying a mattress for the first time. When testing the DreamCloud Luxury Hybrid for Tom’s Guide, Jo said: “I loved the back support and pressure relief it offered. Plus, it looks far more expensive than it is.” When she isn’t writing about sleep, Jo also writes extensively on interior design, home products and photography.

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Walmart’s massive 4th of July sale is my top pick for summer sleep — 3 queen mattresses starting from $154

The Siena Memory Foam Mattress is cheaper than Black Friday in epic 4th of July Amazon mattress sale

Walmart’s selling this queen size Serta mattress for the same price as a twin in the Memorial Day sales

Sleep well with up to $725 on Serta mattress sets this 4th of July

At just $278 for a queen this memory foam mattress deal is a stone cold Memorial Day bargain

5 queen mattresses under $700 I’d buy in the Memorial Day sales to improve my sleep, from DreamCloud, Nectar, and more

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