Considering we spend a 3rd of our lives asleep, it’s crucial to invest in a comfortable mattress with longevity. And with couples who have committed to sharing a bed, possibly the one factor more important than comfort is space. A king-size bed can deliver ultimate relaxation, whether you’re sharing a bed with a partner or you get to have it all to yourself. If you’re looking to buy a king-size mattress, you need to know what the dimensions are so that you can understand how the mattress and its corresponding frame will fit within your room. In this article, we discuss what are the dimensions of a king-size bed mattress, how to choose a king-size frame, and what the benefits of sleeping in a king-size are.

What are the dimensions of a king-size bed mattress?

The short answer to, 'What are the dimensions of a king-size bed mattress?', is that a king-size mattress is 5 feet wide and 6 feet 6 inches long. While a small double (queen) mattress can easily fit two people, being 4 feet wide and 6 feet 3 inches long, the added spaces give you extra space to spread out comfortably without disturbing the sleeper you're sharing the bed with. King size mattresses are spacious, but unlike super king or Alaskan king mattresses, they are not so big that only those with the biggest bedrooms can enjoy them. While this is a typical dimension of a king-size bed mattress, it's worth checking the measurements of each bed you look at as the dimensions could differ slightly between each product.

What size is a super king bed and mattress?

A super king bed and mattress is an indulgent 6 foot 6 inches long and 5 inches wide. Super-king mattresses are favoured by those with large bedrooms and want even more space than what a king-size mattress offers.

King size bed with mattress bundle

Product: Lyla Wrought Iron Bed

What is the largest mattress size?

The largest mattress size is the Alaskan King, which is 9 feet wide and 9 feet long, making it an attractive square shape and a sublime choice for people that appreciate symmetry in bedroom design. As the name suggests, the Alaskan King was named after the biggest state in the US as a tribute to its impressive size. Because of the large up-front cost, most people are put off of Alaskan King mattresses, but if you have the budget and the room for it, then an Alaskan King will certainly make a statement.

How wide is a king size bed frame?

When buying a new mattress, you need a frame to match. Naturally, the frame will be bigger than the mattress itself. You’ll need anywhere from 2 to five inches of extra width to fit the headboard and footboard. In general, you should ensure that your king-size bed frame is at least 76.5 to 78 inches wide.

What are the benefits of a king-size bed mattress?

Purchasing a king-size bed is an investment, but it’s one that comes with several benefits, including:

Extra space

This is the most obvious benefit of having a king-size bed mattress. A king-size bed offers generous room for couples, reducing the risk of you being pushed to the edge of the bed by your other half. A king-size mattress is also big enough to fit two adults and a child, making it ideal for young families.

A great family bed

Do you have a dog (or two, or three) that likes to join you when you go to sleep? Is your family the type to lay in bed watching TV shows together on a Sunday morning, or during the holidays? If this is the case, then a king-size bed might just be the size for you. Not too big, but not too small, a king-size bed mattress is just the right size to have a movie marathon with the whole family.

Improved quality sleep for restless sleepers

People with arthritis and joint pains often struggle to stay in a stationary position for a long period of time. Because of this, people with arthritis or similar conditions tend to be restless sleepers. A king-size mattress provides you with ample breathing room when sleeping to move around without the risk of falling out of your bed or accidentally kicking your partner awake.

Flexible design

You can have a king-size mattress no matter your bedroom design, just ensure that your bedding matches the surrounding interior! Alternatively, if you really want your bed to stand out, why not get bedding that’s independent of your bedroom’s style?

Natural Supreme 5000 Mattress

Product: Natural Supreme 5000 Mattress

What material is better for king size beds?

Beds are made from a myriad of materials. For those that value comfort, it's important to understand what your king-size mattress is made from as this will impact your overall enjoyment of the mattress.

Memory foam

Over the past few years, memory foam has become super trendy and with good reason; it’s so soft and the velvety feel of the material promotes high-quality sleep. A memory foam mattress is made out of polymer polyurethane and a mixture of chemicals, which are the reason for the sinking feeling you get when you first get into bed. Memory foams also mould to the sleeper, making it a good option for those with arthritis and other related conditions.


Some people don’t want that sinking feeling when falling asleep. If you want a mattress that’s firmer and bouncier, then innerspring mattresses are the way to go. However, if you sleep on your side, then an innerspring mattress is not advised.


A king-size latex mattress is one of the most expensive options available, but it’s favoured by those with arthritis and similar conditions because of its responsiveness. Like memory foam, latex shapes itself to match the sleeper’s body, but unlike memory foam, it offers a little more resistance. Because of this, it’s easy to fall into the right position. The firmness of the latex and the extra space offered in king size mattresses make this a good pairing for any restless sleeper.

Endurance Beds

Endurance Beds has been providing people with a good night's sleep for over 13 years. We offer an exciting assortment of king-size mattresses and matching frames that are sure to meet your sleeping requirements. Alternatively, we can also construct a bespoke bed with you in mind. For bespoke or ready-made beds, enquire now here.

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