King vs Full Mattress Sizes: What’s the Difference?

King vs Full Mattress

Standard king and full-size mattresses are very different beds in dimensions. At 76 by 80 inches, king-size mattresses are the largest of the standard bed sizes. Meanwhile, full-size mattresses are much smaller, at only 54 by 75 inches.

Many different factors can impact the mattress size you need. It would help if you went mattress shopping armed with the information to guide you in choosing the right mattress.  

What Is a King Size Mattress?

At 6,080 square inches, the king-size mattress is the largest mattress size by surface area. If you want an even larger mattress, go up to an oversized mattress like a Texas king or a Wyoming king.

Standard or eastern king mattresses were designed to offer couples the most comfortable sleep experience. They are also perfect for taller sleepers or those who have large bedrooms.

King Mattress Size Dimensions

The king-size mattress is the same size as two twin XL mattresses. This is often referred to as a split-king bed, which allows partners to maintain a connection while having the freedom to choose a bed more tailored to their needs and preferences.


  • Spacious for couples
  • Fills out big rooms
  • Well-suited for taller sleepers


  • High-priced range
  • Require larger interior space
  •  Heavier to move

MLILY’s King Mattress: ONYX Pro Hybrid Medium

Those who want a cooling and responsive king-size hybrid should check out the ONYX Pro. Our versatile medium hybrid mattress boasts multiple cooling features as well as responsive and adaptable coils.

The cover of the ONYX Pro features graphene infusions to enhance its antibacterial and cooling capacity to create a pleasantly chilly and hygienic sleep surface. This cover works with the copper gel-infused memory foam comfort layer to draw heat away from your body.

These cooling layers sit on top of a transition layer of Flex Comfort foam and a based layer of adaptable pocketed coils for optimum spinal alignment and support. Best of all, if you want to do a split king, the ONYX Hybrid lineup also features a firm and a plush option!

What Is a Full-Size Mattress?

The full-size mattress, also called the double bed, was initially intended for couples has become sufficient due to the increased height and size of people since the 20th century.

Full-size beds are now recommended for single adults who want more wiggle room than a twin offers.

Full Mattress Size Dimensions

The full bed dimensions are 54 inches wide and 75 inches long. This makes these beds better for sleepers with smaller bedrooms and those shorter than six feet tall.


  • Roomy for single-sleepers
  • Fits in small rooms
  • More affordable


  • Less room for couples
  • More suitable for sleepers below six feet tall

MLILY’s Full Mattress: WellFlex 2.0

Those who want a versatile and cooling full mattress should check out the MLILY WellFlex 2.0. One of our most popular mattresses, the WellFlex 2.0 features layers of cooling foam to keep you from overheating.

The first layer of the WellFlex 2.0 is our Gel AeroFusionTM memory foam. This ultra-breathable foam packs a double whammy of cooling comfort. It circulates cooling air through millions of air pockets, and its gel infusions help draw heat away from your body.

Below, another layer of gel memory foam helps pull body heat even further away from you. All while a transition layer of AdaptiFoamTM and a base layer of Flex Support foam provide fantastic lift and support.

Alternative King and Full Mattress Options

There are several versions of the king-size bed, as well as an alternative version of the full-size bed, that you can choose from if the standard king or standard full is not suitable for you.

Full XL   

If you want the width of a full, but you’re over six feet tall, the full XL might work for you. At 54 by 80 inches, you get the same compactness of the standard-size full bed but an extra five inches of length.

Split King          

The split king mattress is the same size as the standard king. However, with the split king, you take two twin XL mattresses and put them into the same king-size bed frame. This allows each partner in a couple to choose their mattress.

The split king setup can be perfect for couples who prefer different firmness levels, adjustable bed settings, or mattress materials.

California King

The California king-size bed takes four inches off the width of the standard king and adds them to the length for a total dimensions of 72 by 84 inches. This makes the California king mattress the perfect size for extra-tall sleepers.

If you’re well over six feet tall, the California King might be the only mattress in the standard-size run that accommodates you. The California king can also work for couples who like to let their pets sleep at the foot of the bed.

Other Standard Mattress Sizes

Aside from the king and the full-sized beds, there are several other popular mattress dimensions you can choose from.


The twin mattress is 38 by 75 inches, making it the most compact adult mattress size. The twin bed may be the best mattress size for those who sleep in compact spaces like studio apartments or dorm rooms.

Twin XL

The twin XL bed is the same width as the twin bed and the same length as the king, making it 38 by 80 inches. This mattress size could work for taller individuals who need a compact bed.


The queen-size mattress is the smallest mattress size that is comfortable for couples. At 60 by 80 inches, the queen mattress offers much wiggle room for taller single sleepers. The queen bed is also the most common bed size in the US.

Factors To Consider When Choosing Between a King Bed and a Full Bed

You’ll need to consider several factors before you decide which mattress size works best for you. Depending on your room size, height, and other factors, a full or a king mattress may be better.


You will be spending much less money on full bed accessories – such as sheets, pillows, and comforters – than on a king bed because they are smaller.  


Your height can impact your mattress needs. If you’re under six feet tall, you can sleep on virtually any mattress you want. If you’re over six feet tall, you likely need a king for the extra height, and those well over six feet may even need a California king-size mattress.

Number of Sleepers

Single sleepers should be happy on a full bed, but couples who share the bed will likely need more room for more comfort.


King-size mattresses are almost always more expensive than comparable full-size mattresses. Those shopping on a budget may find the full-size bed more within reach.

Room Size

You’ll need to ensure your bedroom is large enough for a king. To facilitate movement around your bedroom, you’ll need at least two feet of clearance around three sides of your bed.

If your bedroom can’t allow for this amount of clearance plus all your other furniture, like your dresser and nightstands, you might need a full instead of a king bed.

Bottom Line

King and full-size mattresses both come with their advantages and drawbacks. Whichever size you choose, remember to get the highest quality mattress that fits into your budget. That way, you can enjoy an amazing night’s sleep every night!

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