King Size Mattresses
King size mattresses are perfect for couples or taller sleepers who need extra space. Choose from memory foam, hybrid, or natural fillings to match your sleep style. All with free next day delivery and a 60-Night Trial. Shop leading brands like Silentnight, Sealy, Hypnos, and Sleepeezee.
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SleepSoul Heaven 1000 Pocket Gel Mattress
Was £324.95
RRP £479.99
Mlily Bamboo+ Memory 800 Pocket Mattress
Was £404.95
RRP £760.00
Silentnight Ortho Dream Star Miracoil Mattress
Was £338.70
RRP £450.00
Sealy Steeple Ortho Plus Mattress
Was £549.95
RRP £779.00
Hypnos Hemsworth Deluxe Mattress
Was £704.95
RRP £1,185.00
Sealy Posturepedic Elevate Blackwood Mattress
Was £1,069.95
RRP £1,729.00
Gainsborough Mayfair 1000 Pocket Ultra Firm Mattress
Was £554.95
RRP £599.00
Silentnight Athens 1400 Mirapocket Ortho Mattress
Was £499.95
RRP £602.00
Emma Helix Hybrid Mattress
Was £1,029.00
RRP £1,499.00
Harrison Spinks Quilted Fusion 4000 Pocket Mattress
Was £1,089.95
RRP £1,559.00
Silentnight UltraGel 1000 Mirapocket Pillow Top Mattress
Was £819.95
RRP £959.00
Simba Earth Escape 4800 Wool Mattress
Was £1,684.95
RRP £1,799.00
Millbrook Wool Ortho 1000 Pillow Top Mattress
Was £684.95
RRP £1,048.95
SleepSoul Celest 2000 Pocket Pillow Top Mattress
Was £549.95
RRP £1,229.99
Emma Diamond Hybrid Mattress
Was £1,109.00
RRP £1,619.00
Silentnight UltraGel 2000 Mirapocket Mattress
Was £979.95
RRP £1,179.00
Sleepeezee Deluxe 1000 Pocket Mattress
Was £479.95
RRP £599.00
Memory Zone 2000 Pocket Mattress
Was £559.95
RRP £799.00
Harrison Spinks Luxury Essential 750 Pocket Mattress
Was £644.95
RRP £859.00
Rock Hard Ultra Firm Mattress
Was £404.95
RRP £600.00
How big is a king size mattress?
Our king size mattresses measure 5' x 6'6" (150cm x 200cm) - ideal for taller sleepers, couples, or anyone wanting more room to stretch out in comfort.
How firm are king size mattresses?
Our king size mattresses come in a full range of firmness levels:
- Soft-medium - gentle cushioning
- Medium - balanced support for most sleepers
- Medium-firm - ideal for couples with different sleep styles
- Firm - great for back sleepers
- Extra firm - our most supportive feel
Need help deciding? Check out our mattress firmness guide for expert advice.
What king size mattress brand should I choose?
We offer king size mattresses from the UK’s most trusted brands, plus our own value ranges.
Looking for unbeatable value? Try:
- Komfi - long-lasting comfort at a great price
- Bodyshape - supportive and reliable comfort
- Luna - simple comfort with unbeatable value
Explore our mid-range king size mattresses from brands loved across the UK, and around the world:
- Silentnight - the UK’s number one mattress brand
- Sealy - posture-focused support backed by science
- Sleepeezee - Royal Warrant holders with 100+ years of heritage
- Millbrook - handcrafted with natural materials in Hampshire
- Emma - multi-award-winning memory foam technology
- Simba - hybrid innovation for restless sleepers
- Relyon - handcrafted British comfort since 1858
Choose from our premium king size mattresses built for ultimate indulgence:
- Hypnos - Royal Warrant holders with eco-conscious craftsmanship
- Harrison Spinks - 100% natural fillings and advanced pocket springs
- TEMPUR - NASA-recognised pressure relief for next-level comfort
How much should you pay for a king size mattress?
King size mattress prices vary by brand and the materials used, and we’ve got options for every budget:
- Budget: from £200 - cheap king size mattresses that deliver great value and everyday comfort
- Mid-range: £400-£600 - enhanced support and extra features for blissful sleep
- Premium: £600-£3,300+ - luxury comfort from leading brands with handcrafted quality
At Mattress Online, we’re committed to bringing you the best value at every price point – from cheap king size mattresses to premium models. Shop our latest king size mattress sale for even better deals.
Do your king size mattresses come with a warranty?
Yes, every king size mattress includes at least a 1-year warranty or guarantee, with many offering up to 10 years of coverage.
You can sleep easy, knowing you're protected for years to come.
Can I get a king size mattress with next day delivery?
Absolutely. Order your new king size mattress before 4pm for free next day delivery across most of the UK.
- Delivery 7 days a week
- Choose your preferred delivery date at checkout
- Handled by our expert local or national teams
Advice and buying guides
See what our customers say about us
Why buy from Mattress Online?
Free delivery to most locations
Free next working day delivery on most of our mattresses and beds, or upgrade to weekend delivery.
Free 60-night mattress comfort trial
Test your mattress for 60 nights and if you don't like it, simply swap it.
Old mattress disposal
We can collect and recycle your mattress - saving it from landfill.
Sales Enquiries
Mon-Sat: 9:30am - 5:30pm
Sunday: 10am - 4pm
Customer Service
Mon-Sat: 9:30am - 5:30pm
Sunday: Closed
customerservice@mattressonline.co.uk
