King vs Full Bed: What's the Difference?

A king mattress is 76 inches wide by 80 inches long, while a full mattress is 54 inches wide by 75 inches long.

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There’s a lot to consider when selecting your dream mattress: firmness, breathability, support, and the big factor (or the small one) — size.

Most mattress sizes are standardized to help you find the right sheets, pillows, and bed frames for your pick. But there’s no dedicated mattress school that teaches you what each size is, and how to choose the one that meets all of your standards. 

Don’t lose any sleep over mattress sizes — Casper is here to help.    

In this article, we’re sinking into the timeless full vs king size bed debate. Their physical dimensions differ, but so do their suitability for both single sleepers and couples. Will your bedroom feel complete with a full, or are you in need of a royal touch? Keep reading to find out. 

What is a King Bed?

A king bed is a standard mattress size that most retailers carry. It’s often the largest mattress size offered, though larger variations do exist (which we’ll cover below). 

The precise dimensions of a standard king size mattress, also known as an Eastern king, is 80 inches long and 76 inches wide.¹ If you like to think in feet, that’s roughly six and a half by six. 

Pros of a King Bed

King beds are crowned royalty for a reason — they’re big. 

The grand size of king mattresses can offer several appealing benefits, especially for sleep partners, such as:

• Extra wiggle room – If you and/or your partner are restless sleepers, you’ll be able to fit comfortably on your respective sides without disturbing the other. No defensive pillow walls needed to shield you from rogue knees or elbows in the night. A study that objectively measured sleep in 8,214 users with bed partners found that compared to sleeping on a full-size mattress, sleeping on a king-size or California king mattress resulted in a 13.3-minute increase in total sleep time, a 4.3-minute increase in REM sleep, and a 2.0-minute increase in deep sleep.²

• Accommodations for children and furry friends – You can comfortably fit a child and most pets on a king bed without having to worry about rolling over onto them in the night, or having them hog your space. For even more room at the foot of the bed, you can opt for a California king, which takes four inches off the normal king’s width and adds to the length. 

• Prime lounging space – Staying in bed all day sounds much more enjoyable when you have a king-sized mattress. You can easily fit a breakfast tray in the center of the bed and still have plenty of room for you and your partner to stretch out wide. (Just mind the comforter. It was a wedding gift.)

Sometimes, size alone isn’t enough to prevent sleep disturbances from a restless sleep partner. For more sound sleep all night long, try the Dream Max from Casper. The seven zones of support perfectly cradle your curves, and the individually pocketed Flex Coils reduce motion transfer from tossing and turning. And of course, it comes in a standard king size, as well as California king, too. 

Cons of a King Bed

The main advantage of a king bed can also be the main disadvantage—it all depends on the size of your bedroom.

If floor space matters more to you than sleeping space, you may decide against a king.

What is a Full Bed?

A full bed falls in the middle of the standard mattress size spectrum: it’s larger in width than a twin,  and smaller than a queen bed in both length and width. 

The exact mattress dimensions are: 75 inches long and 53 inches wide.¹ That’s a little over 6 feet by four feet. 

Some people may refer to a full bed as a double bed, but don’t confuse this to mean that a full bed is the sum of two singles, or twin beds. It’s not. 

Pros of a Full Bed

Full beds offer the full mattress experience:

• Extra space for single sleepers – Full beds are a big(ger) step up from a twin, offering an extra 15 inches in width. 

• The best of both worlds – Full beds are very space efficient: you get a little extra sleeping space without your bed taking up the entire room. 

Cons of a Full Bed

Full beds pose the biggest disadvantages for couples. Split down the middle, each partner has exactly 26.5 inches of mattress space to occupy. That’s about the length of an average pillow.¹ If you’re not a cuddly couple, these close quarters may lead to some sleepless nights. 

Do Two Full Beds Make a King?

The quick answer — no. 

Two full beds pushed together would be 106 inches wide — that’s 30 inches wider than a king, and two inches shy of the width of an Alaskan king. If you’re moving in with a partner and considering merging your two full mattresses, keep these bed dimensions in mind. 

Two beds that do make a king? Twin XLs. Learn more about twin XL vs full mattresses in our blog.

Suitability of a King vs Full

Do you want to rule the bedroom with a king, or would all your needs be fulfilled with a full?

First and most importantly, compare the size of your potential mattress to your bedroom’s size. Be sure to ask yourself³:

• Will you have at least three feet around the foot and sides of the bed? 
• Will you be able to open all bedroom doors, drawers, and closets easily?
• Will other bedroom necessities fit in the room, like nightstands, dressers, or desks?
• How easy will it be to make the bed in the morning?

Then, consider your current sleeping arrangement and sleep habits: 

• Are you a single sleeper, or do you have a partner with whom you share a bed? 
• Do you sleep in bed with your children or pets? 
• Do you enjoy a nice cuddle, or do you appreciate your space? 

Now, let’s look at each option individually to see who benefits most.

Who Should Choose a King Bed?

Unless you really enjoy splaying out (and you have the bedroom space), single sleepers don’t necessarily need a king bed. Kings are designed with more than one person in mind, or couples where one or both partners:

• Like to have their space
• Tend to toss and turn in bed
• Are taller and need a longer mattress

Who Should Choose a Full Bed?

King beds are objectively bigger than fulls, but that doesn’t mean they’re better. Full beds are the perfect option for: 

• Singles who want space – Do you like to stretch your limbs out like a starfish in the center of the bed? A full mattress can accommodate wide sleeping positions better than a twin. Read more about full vs twin mattresses in our blog.

• Cuddly couples – If you and your partner love to spoon and snuggle as you drift off, you may be satisfied with a full bed. 

If you and your partner are on opposite sides of the king vs full bed debate, consider your sleeping habits and preferences. Sharing a bed is all about compromise; think of this as a test in communication. 

Variations of King and Full Beds

Almost all retailers offer both standard kings and fulls, but you can often choose custom variations if the originals don’t perfectly meet your mattress needs. 

Some variations are harder to find than others; keep in mind that you’ll need to also pick out matching sheets and a bedframe.

King Bed Variations

Do you like the idea of having a king bed, but the standard dimensions simply aren’t doing it for you? Maybe you’re especially tall and need extra room at the foot of the bed, or you have the bedroom space for something bigger, so you might as well fill it.

Luckily, there are several variations on the classic king bed, each more regal than the last. Here are a few examples and their dimensions (length x width, in inches)¹:

• California king – 84 x 72
• Texas king – 98 x 80
• Wyoming king – 84 x 84
• Vermont king – 96 x 96
• Alaskan king – 108 x 108

Learn more about the biggest bed size in our blog.

Another popular king bed variation that isn’t related to size is known as a split king. Split kings are essentially two twin XL beds placed together on a king-sized bed frame.² The appeal of these Frankenstein beds is two-fold:

1. Partners with opposing preferences can choose a mattress with the exact firmness and support they want.

2. The motions of a restless sleep partner won’t transfer as easily to the other side of the bed, since they’re technically two separate mattresses. 

At Casper, we offer all of our mattresses in both California king and split king variations to satisfy every sleeper. Check out our blog to learn more about the king vs split king mattress.

Full Bed Variations

Unlike king beds, full beds only have one main variation: a full XL. 

If you’ve ever lived in a college dorm — or bought sheets for your child ahead of their college move – you’re probably familiar with a twin XL bed. The “XL” refers to the mattress’s extra length in comparison to the standard mattress size. 

The same concept applies to a full XL. It’s five inches longer than a normal full bed, putting the dimensions at 80 inches long and 53 inches wide.¹

For people over 6 feet who tend to “hang ten” off the end of the bed, those extra few inches make a big difference. 

Find Your New King or Full Bed with Casper

No matter where you land on the king vs full debate, Casper has you covered. 

Our mattresses come in all the standard sizes, including a few popular variations. But at Casper, size is only the beginning. 

Each mattress is designed to solve the most common sleep problems. Need premium support for muscle pains and restlessness? Choose the Dream Max orthopedic mattress. Want to stay cool even during sweltering summer nights? Opt for the Snow Max cooling mattress. And for a mattress that can keep all sleep partners happy, try The One memory foam mattress. 

Take our sleep solutions quiz to find the best mattress for you, or visit a Casper Sleep Shop to speak with one of our Sleep Specialists today. 

Sources: 

1. National Council on Aging. Guide to Mattress Sizes and Dimensions. https://www.ncoa.org/adviser/sleep/mattress-sizes/ 
2. U.S. News. What Is a Split King Bed? https://www.usnews.com/360-reviews/sleep/mattress/what-is-split-king-bed 
    Sleep Medicine. The association between mattress size and objectively measured sleep in 8,214 users with bed partners. https://www.sciencedirect.com/science/article/pii/S138994572200449X
3. Wirecutter. How to Pick the Right Size Mattress for Your Bedroom. https://www.nytimes.com/wirecutter/blog/how-to-pick-the-right-size-mattress-for-your-bedroom/