What Size is a King Size Mattress? - Inn Mattress

A king size mattress is the largest commonly available mattress size. With extra width and length compared to other mattress sizes, king size beds provide ample room for couples or individuals who like to spread out at night. But what exactly qualifies as a standard king size mattress when it comes to dimensions?

Standard King Mattress Dimensions

The standard king mattress size is 76 inches wide and 80 inches long (about 6 feet 4 inches wide and 6 feet 8 inches long). This makes a king size mattress a full 16 inches wider than a queen size mattress.

While a king mattress is the same length as a queen, the extra width allows more freedom of movement without fear of falling off the edges. It also provides enough room for a couple to sleep comfortably while still having space between them.

Some key details on standard king mattress sizing:

  • Width – 76 inches
  • Length – 80 inches
  • Total surface area – 6,080 square inches (about 42 square feet)

So in summary, a standard king size mattress in the United States is 76 inches wide by 80 inches long. Mattresses labeled as simply “king” will adhere to these dimensions.

Other King Size Mattress Variants

While the standard 76 x 80 inch king size is by far the most popular, there are a few other mattress sizes that qualify as “king” beds:

California King

A California king mattress is 72 inches wide and a lengthy 84 inches long. The slightly narrower width coupled with 4 extra inches of length makes a California king well-suited for very tall people who need more leg room.

But the reduced width may be an important consideration for those who still want to comfortably sleep two people across the mattress.

Split King

As the name suggests, a split king mattress is essentially two mattresses designed to fit perfectly side-by-side as one unified bed surface. This allows couples to customize the firmness to their individual preference while still having a traditional king-sized mattress area to share.

Split king mattresses are made from two XL twin size mattresses pushed together. So each half is 38 inches wide by 80 inches long. Combined they equal the standard 76 inch king width.

Alaskan King

On the opposite end of the size spectrum from split kings, Alaskan king beds are truly massive. They measure 108 inches wide by 108 inches long – bigger than most bedrooms can accommodate.

Alaskan kings are primarily a novelty item for those who really want to go all-out, and have the room to match.

Buying Considerations for a King Size Mattress

King size mattresses provide ample room for couples or individuals who like to spread out. But there are a few important factors to keep in mind when shopping for a king bed.

Bedroom Size

Before buying a king mattress, make sure your bedroom can comfortably fit it. Ideally there should be at least 2 feet of space between the edges of the mattress and adjacent walls.

The recommended minimum bedroom size for a king bed is around 12 x 12 feet or 144 square feet.


Good quality king size mattresses typically range from $1000 on the low end up to $3000 or more for premium models. The price depends on the quality of materials used, mattress type, special features, and more. Be sure to find the right balance of size, comfort, and price for your needs.

Firmness Preference

King size mattresses are available in a range of firmness levels from extra firm to plush to accommodate different sleep positions and body types. In general, medium firmness tends to suit most sleepers. But do some research to determine what firmness you need before deciding on a particular king size mattress.

Special Features

Today’s mattresses offer innovative features like advanced cooling systems, edge support reinforcements, pressure relieving materials, and more. Consider what features will improve your sleep experience when shopping for a king size bed.

Mattress Type

Memory foam, innerspring, latex, and hybrid king size mattress models all provide different benefits. Understand the pros and cons of each main mattress type when deciding what’s right for your needs.

Finding the Best King Size Mattress

With the right considerations in mind, you’re ready to start shopping for a top-notch king size mattress. Focus on finding a model from a reputable brand that offers the ideal blend of size, comfort, support, and durability to meet your needs.

Take advantage of sleep trials and warranties to take some risk out of the purchase. And don’t hesitate to ask mattress retailer associates for advice if you need guidance finding that perfect king size bed.

Investing in a quality king size mattress is an excellent route to improving sleep comfort and quality for years to come. Take your time, understand the different size options and buying considerations, test some mattresses, and choose a model that feels just right. Sweet dreams await!

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