King Size Mattresses

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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.

Advice and buying guides

Choosing the right king size mattress

We want you to be confident knowing which king size mattress will suit your needs. This guide will help you understand what you want to look for.

Is a king size mattress right for me?

When we think of the sleeping space that a king size mattress gives you, it measures 15cm (6in) wider and 10cm (3in) longer than a double mattress. This extra space can make a huge difference in your sleep quality. If you sleep with a partner, the last thing you want is to be balancing on the edge of your mattress to give yourself enough space to sleep.

You also want to avoid disturbing each other when you or your partner turn in the night. A king size mattress gives you a larger sleeping space allowing for more of the motion to be absorbed into the mattress. The extra length can be just what's needed if you're tall and often find your feet dangling off the end of the bed.

Another consideration is that if you have a king size storage bed, it will give you extra space to put things away and reduce the clutter.

Of course though, not everyone has the physical space to buy a king size mattress and bed. You will probably want a minimum of 30cm (12in) of space around your bed to get in and out, or 50cm (20in) to accommodate the average size of a bedside table.

But if you can make the jump to a king size mattress, it's well worth it. If you don't already have a bed to go with your new king size mattress, then we offer a great selection of king size divan beds, bed frames and storage beds.

If you're looking for some additional luxury and an extra 30cm (12in) of sleeping space, then do consider a superking mattress.

How big is a king size mattress?

A king size mattress is 150cm (5ft) wide and 200cm (6ft 6in) long and offers a very premium sleeping space. The only larger size that we sell is the superking. The size is standard between beds and mattresses made in the UK. So if you have a king size bed, a king size mattress will fit.

Will a king size mattress fit my bed?

Sometimes you might be unsure what size bed you have. Using a tape measure you can see if it is 150cm wide and 200cm long. If you're measuring your existing mattress, this can vary by around 2cm which is fine.

If you can't find the size of your bed in our listing, then it might be a European sized bed. We do sell European king size mattresses as well as other European sizes. If your bed was manufactured abroad, then you might have queen mattress size or any other non-UK size mattress. In this case, you will most likely need to replace the bed to fit a new mattress.

What base do I need for a king size mattress?

Most beds either come with wooden bed slats or a solid base. All our king size mattresses will work perfectly with either type of bed base.

If you do have wooden slats, then it is recommended that the space between the slats should be less than 7.5cm to avoid any sagging through the gap. See our bed slat guidance to learn more about the maximum gaps between your bed slats specific to each mattress brand.

Choosing the right brand for your king size mattress

We're proud to work with the best mattress brands in the UK to give you the perfect range to choose from. If you're not familiar with any particular brand, it can be difficult to know what they offer and why you should choose them.

Silentnight

Silentnight is renowned for exceptional quality from 75 years of innovation and expertise. They offer many award winning mattresses with a wide range of pocket sprung, memory foam, zoned Miracoil® springs and orthopaedic king size mattresses. Budget wise, you'll find a great selection of affordable premium king size mattresses as well as many entry level king size mattresses.

Sleepeezee

Sleepeezee have been making luxury beds since 1924 and pride themselves on expert craftsmanship and premium standards. They offer a wide selection of king size pocket sprung mattresses, memory foam mattresses and orthopaedic mattresses. While they are known for their luxury mattresses, they also offer a selection of budget friendly king size mattresses.

Sealy

A world renowned mattress brand with their innovative PostureTech core spring system. They are ideal if you are wanting to invest in a high quality king size mattress with great posture support. You'll find many king size spring mattresses to choose from as well as a selection of memory foam layers. You'll be able to find a Sealy king size mattress to suit any budget.

Harrison Spinks

Harrison Spinks pride themselves on combining luxury, handcrafted quality and comfortable sleep made from the finest natural materials. You'll be hard pressed to find a better quality than a Harrison Spinks king size mattress.

This is just a sample of the many mattress brands to choose from.

What type of mattress do I need?

There are quite a few options to consider when choosing the type of king size mattress to purchase. We can simplify this into the support system, comfort layer and additional benefits.

Support system

A pocket sprung king size mattress are our most popular choice. Your weight is spread across individually cased springs that give you support just where you need it. It's generally the case that a larger spring count can provide more refined and durable support. Some mattresses may use multiple layers of springs to provide both support and comfort.

Standard sprung king size mattresses have springs that are interconnected and topped with a variety of comfort layers. This is often referred to as an open coil spring system as the springs aren't in pockets like pocket sprung mattresses. The advantage of a standard sprung mattress is that it can keep costs down for your new mattress purchase.

Reflex foam king size mattresses has become increasingly popular in king size mattresses as a highly resilient and supportive mattress core and is often used to replace springs. As a rule this foam base is made of high density polyurethane foam, offering a wide range of benefits from increased mattress stability, reduced partner motion transfer and improved pressure relief, especially when combined with memory foam, gel or latex.

Comfort layer

Memory foam king size mattresses are a popular choice for your comfort layer. Support and comfort is provided by the foam layer. The foam uses your natural body heat to mould to your unique body shape, while allowing for airflow to regulate your temperature. This gives you tailored support for your sleeping position, even if you turn in the night.

Latex king size mattresses are a natural alternative to memory foam with the benefit of responding to your body shape faster. Latex mattresses are usually more expensive than a memory foam equivalent.

Hybrid king size mattresses generally use memory or gel foam in conjunction with a pocket sprung support system. The memory foam acts as the comfort layer while the spring system provides the support.

Fibres, such as Silentnight's Eco Comfort Fibre, as well as foam, are a great way of providing comfort. They are often paired with a spring support system.

Natural filling king size mattresses are a great choice as they are intrinsically comfortable and provide more hypoallergenic and sustainable benefits. These fillings can be from a range of wool, cotton, cashmere or silk providing the most luxurious comfort on a mattress.

Pillow top king size mattresses provide an extra layer of comfort to give your mattress a nice plush feeling, without compromising the support system. So if you want the firmness, but like the feeling of being in the bed rather than on it, then consider upgrading to a pillow top mattress.

Gel memory king size mattresses are an advanced memory foam that improves sleep with a faster bounce back when moving in the night. They rely on gel beads to contour to the sleepers body shape which is quicker than a memory foam equivalent which uses body heat. Gel mattresses have inherent cooling abilities that draw heat away from your body, helping to keep you at an optimal temperature during the night.

Additional benefits

Orthopaedic king size mattresses (or Ortho mattresses) are generally on the firmer side and are designed to enhance your spinal alignment and provide joint support. Our orthopaedic mattresses are ideal if you suffer from back pain.

Some mattresses are single-sided and some are double sided. It's recommended that you rotate your mattress every couple of months to increase the lifespan of your mattress by alternating the places that will get most use. Some mattresses mirror the internal components which means they are double sided and can be flipped in addition to rotated. This is great for preserving the performance of your mattress for years to come.

How firm should my king size mattress be?

When we try a mattress in a store, we are often testing out the firmness of the mattress. However, the feel of the mattress may not directly mean you have a restful and healthy sleep. Here’s a guide to help you make a decision:

Soft-to-medium firm mattresses

These are great if you know you love that sinking feeling when you lay on your mattress. If you're light (around 60kg and under) then a softer mattress will help ensure that you're getting the right support across your body. A softer mattress can also relieve pressure which may improve your circulation. If you have wide shoulders or hips and like to sleep on your side, a soft mattress can help you keep your spine aligned.

Firm and extra firm mattresses

These are great if you're a front sleeper as it will help maintain your body position in a more natural way. If you suffer from back problems then a firmer mattress is usually recommended. This is why our orthopaedic mattresses are often on the firmer side. If you're heavier or concentrate your weight in a specific area then a firmer mattress will be ideal to stop you sinking into the mattress and misaligning your posture.

Medium firmness mattresses

This is the most popular firmness choice where it's neither too soft nor too firm. They're great for back and side sleepers and when your partner has a different body weight to you. If you want that soft mattress feeling, but also to ensure you have the right support system, then a medium mattress is a great choice.

If the mattress is for a child or teenager who is still growing, then maybe consider a medium-firm mattress to ensure they have great spinal alignment as they grow.

What if I choose the wrong firmness?

We understand that it can be hard deciding on the right firmness for your new mattress. This is why we offer a comfort trial on all our mattresses. It may take a few weeks to fully feel comfortable on a new mattress, but if after 30 nights it just isn't right, let us know and we'll swap it for another mattress free of charge - you just pay the difference if you upgrade to a more expensive mattress. Just remember to use a mattress protector to protect the mattress.

How much should I spend on my king size mattress?

We offer a lot of mattresses at various different price points.

Our budget king size mattresses usually start around £200. They'll provide great support and comfort for the price and usually are made from springs or foam. These are a good choice for those who want great value or are looking for a cheap king size mattress for a guest bedroom.

If comfort is your priority, then around the £400 range you can get some fantastic pocket spring support systems with additional comfort layers and fabrics. These mattresses will give you individually zoned support making it ideal for couples who don't want to disturb each other at night.

Our premium mattresses take your comfort to the next level. You'll find more advanced support systems and additional comfort layers using natural materials. These mattresses combine the level of comfort with the support that will enhance the quality of your sleep. Our premium mattresses can range anywhere between £600 to £1,200.

Finally we come to our most luxurious and prestigious king size mattresses. These make no compromise, providing you with the best zoned sleep support, luxurious and natural fillings, and premium materials to the touch. The craftsmanship of these mattresses are unmatched and you'll consider this mattress a real investment into the most luxurious and healthy sleep you can get.

We are among the largest stockholders of king size mattresses in the UK. We work very closely with our manufacturers to offer you the best possible price. Check out our king size mattress sale for the latest deals and offers on your next king size mattress.

Buying a king size mattress from Mattress Online

We've been selling king size mattresses for over 20 years, so we know how to get them to you quickly and carefully. We stockhold hundreds of different product ranges so you can be sleeping on your new mattress as quickly as tomorrow.

All our mattresses come with free standard delivery on a day of your choice to most locations within the mainland UK. A number of our king size mattresses are eligible for a free upgrade to premium delivery where they'll be delivered to a room of your choice. Alternatively you can choose to upgrade to premium delivery on any of our mattresses. Please refer to our delivery information for specific details about our delivery services, prices, any associated fees, longer delivery times or areas we are unable to deliver to.

Recycling your old mattress is extremely simple. You can upgrade to this service when you checkout. We'll swap the old mattress with your new one giving you confidence that your old mattress has avoided landfill. Please refer to our mattress recycling information for the latest pricing information.

All our mattresses come with a minimum of a 60 night comfort trial. If for any reason you don't like sleeping on it, you can swap it for another one after 30 days.