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Bed & Mattress Sizes Guide

Bed & Mattress Sizes Guide


Bed sizes and mattress sizes are two very important dimensions to be aware of when shopping for either. Mattress dimensions are usually nearly identical except for varying in overall thickness. Bed dimensions vary wildly and can cause some confusion. This guide is meant to help understand what numbers to look for and which ones to ignore.


  • Bed frames often list overall dimensions, not inner dimensions
  • Mattress width and length (depth) are similar between brands
  • Mattress height (thickness) varies wildly between brands
  • Looking at the bed size name (e.g. Queen, King, Twin) is the safest approach
  • Only Twin XL box springs work with a king-size mattress—not regular Twin size


Bed sizes, depending on the manufacturer and design, will have width, depth, and height dimensions that vary tremendously. Bed frame sizes listed here are rough estimates based on an average of several different designs. The largest variance in dimensions, for both beds and mattresses, is seen in the height dimension. This is easily understood when one considers that many different beds are many different heights and that many different mattresses are many different thicknesses (heights).

California King Size

King size bed diagram HomeRefinery
Californian King Mattresses and beds accommodate couples, as well as single-sleepers, that want a little more foot room.

The California King bed is an often misunderstood bed size that’s actually slightly narrower than standard king size beds but four inches longer. This bed size first became popular on the West Coast of the United States as a custom-designed size popular among movie stars and the Hollywood Elite. After several decades of marketplace evolution the California King, Queen, and King size mattresses have all become standard options in the bedding industry. Read our article California King vs Regular King: What’s the Difference? for a complete overview of what makes this mattress and bed size unique.

Bed Size: 80.5″ x 89.3″

Mattress Size: 72″ x 84″

King Size

King size bed diagram HomeRefinery
King Size beds offer couples ample space to flounder about and extra room for pets

The King size mattress and bed is was developed in the late 1950s as an upsell to the then-standard Twin size. This was marketed alongside research suggesting that Americans, as a collective, were growing taller on average. The King size mattress was heralded as a refinement suited for modern families in modern society. After another decade of support from such groups as the National Association of Bedding Manufacturers, the King size bed was officially mainstream and rapidly-growing in popularity. Today, the king size is regarded as a standard option for both beds and mattresses.

Bed Size: 79.5″ x 88.9″

Mattress Size: 76″ x 80″

Queen Size

Queen size bed diagram HomeRefinery
Queen Size beds are popular options for adults with sleeping partners that like close-quarters positioning.

The Queen size mattress also became standardized during the late 1940s and 1950s alongside the king mattresses. The Queen size was considered a hefty upgrade for single sleepers and a simpler alternative to putting two twin mattresses side-by-side, a common practice by couples of that era. While many custom mattresses existed at the time, the standardization to Queen and King allowed furniture makers to offer commercial options. For example, placing two twin size mattresses together would offer couples a wider sleeping area but they were unlikely to find a bed frame to cater to that size.

Bed Size: 64.5″ x 86.125″

Mattress Size: 60″ x 80″

Full Size

Full size bed diagram HomeRefinery
Full size beds are ideal for teenagers and smaller adults, but can also accommodate two sleepers in a pinch.

The Full-size option is popular for adults, that sleep by themselves most nights when space is a key factor. For example, a full-size mattress is six inches narrower than a queen and six inches shorter. For people of average and below-average heights, this bed size is often an attractive choice. There are fewer beds and mattresses on the market for this size but not so few that one should feel discouraged from looking. This bed is often referred to as a “double bed” and is a popular choice for teenagers and college-aged adults.

Bed Size: 79″ x 88″

Mattress Size: 39″ x 80″

Twin Xl Size

Twin XL size bed diagram HomeRefinery
Twin XL bed sizes are the go-to for college dorms and are designed for single person sleeping.

The Twin XL is nearly identical to regular twin size beds—the only difference being an extra six inches in overall length. Twin beds are the go-to choice for youth beds, including most bunk beds, but are often abandoned in late teenage years and early adulthood. College dorm rooms utilize the Twin XL for two reasons; the first being their smaller width and the second being a suitable universal length to simplify the procurement process across campus. After all, it’s much easier for colleges to manage to order 20,000 of the exact same product rather than catering to 3-4 different sizes.

Bed Size: 79″ x 88″

Mattress Size: 39″ x 80″

Twin Size

Twin size bed diagram HomeRefinery
Twin Size Beds are the go-to choice for children and preteens.

The Twin size is the standard youth mattress and is a popular choice for kids around the world. This bed and mattress size is common to trundle beds, bunk beds, and even day beds. These mattresses were popular for adult sleepers in the early parts of the 20th century but, as the average size of Americans started to increase, they were replaced by the newly-popularized King and Queen size beds. In today’s world, twin size beds are seen almost exclusively in kid’s rooms.

Bed Size: 44″ x 88″

Mattress Size: 39″ x 74″

Bed Size vs. Mattress Size: What’s the Difference?

Bed Size vs. Mattress Size Comparison Chart Homerefinery
Mattresses have very standardized sizes and are made to fit inside bed frames. Bed frames often have considerable variations in overall dimensions—but accommodate standard mattress sizes regardless.

Arguably the most important consideration to make when picking out a bed or mattress is to stop and make yourself aware of some basic dimensions. This may seem arbitrary—even silly—but will help throughout your entire shopping process. We’ve hammered through plenty of mattress reviews to find the best mattress in each category but all will be for naught if we can’t help ensure you order the right size for your bed! Below are some of the simplest of these ideas with a bit of elaboration to help understand why they’re so important.

Mattresses are Smaller than Bed Frames

In most cases, you’ll find that mattress dimensions are going to be less than bed frame dimensions. This means king size bed dimensions are slightly larger than king size mattress dimensions. This is because a mattress has to fit inside a bed frame! Notable differences are platform beds and Murphy beds.

Box Springs Raise Mattress Height

Many shoppers complain of their mattresses being either too low to the ground or too high from the ground. In most cases, this issue can be resolved through the addition or removal of box springs. Box springs are usually offered as an add-on by mattress retailers but rarely included. Box springs have a very negligible impact on overall mattress comfort so if you’ve already got a set—use those for your new mattress! Just know; a mattress you’ve tried in the store may not have the same height in your home without box springs.

Exact Bed Dimensions May Vary

Bed frames aren’t governed by as rigid of sizing guidelines as mattresses. The overall dimensions of a bed frame may vary wildly between design and manufacturer—even for the same size bed frame. That means that the king bed dimensions from one furniture brand may be entirely different than the king bed dimensions from another. Don’t stress about this—unless otherwise stated each bed frame size has been designed to accommodate that size of a mattress, regardless of that bed frames specific dimensions.

Bed Frames Come In Adult And Kids

You aren’t likely to find this written anywhere on a retailer’s website, but bed frame designs aren’t always available as King, Queen, Twin, and Full sizes. In many cases, manufacturers design bedroom collections for either adults or kids—kids furniture is often referred to as a ‘youth collection’ by designers. Before you get your heart set on any bed design make sure it is available in a size that will accommodate the mattress you plan to use it with.

Common Questions

From time to time, we find that our readers run into the same problems. In such cases, we try to build resources to better understand specific issues. This article was one such effort, but we felt charts and explanations of bed and mattress sizes didn’t fully address common concerns. Below, you’ll find several common questions and concerns that often plague the mattress-buying process.

Can I use Twin size box springs for my King Size mattress?

No. King size mattresses can accommodate non-King size box springs in most cases but not all. Two twin mattresses are the same width as a king-size mattress but not the same length. Only two Twin XL size box springs can be used to substitute for King Size box springs.

Can I flip my Mattress Over?

Maybe. Some mattresses are designed to be flipped over and some are not. Flippable mattresses feature comfortable materials on both the top and bottom, often in varying degrees of firmness.

Layla Sleep’s two-sided memory foam mattress is a good example of one such design. You have a layer of memory foam on top designed to provide a medium-firm feel and one layer of memory foam on the bottom designed to provide a firm feel.

Most memory foam mattresses have a much denser base layer of foam on the bottom that would not be comparable to the comfort of the top layer. However, this layer would still be somewhat sleepable in our opinion, if you were in a pinch.

Other mattresses, such as traditional spring mattresses, aren’t designed to flipped and often contain very uncomfortable materials on the very bottom. Sleeping on the bottom side of a one-sided mattress could damage the top side. Always check with the manufacturer.

About the Measurements

The bed and mattress measurements that were included in this article are to provide an average illustration of dimensional differences between standard sizes. It’s important to recognize the context of these numbers, and that bed sizes vary much more so than mattress sizes.

For example, each mattress we compared for this article had the exact same with and length/depth measurements for the available sizes. The height/thickness measurements varied considerably but, as a general rule, mattress sizes are the same regardless of brand.

On the other hand, beds and bed frame dimensions can vary wildly between different brands. Much like mattresses, bed frames are usually most different in their height, but overall width and depth/length varies considerably as well. As a general rule, look at the specified size of a bed rather than the actual dimensions to be sure that your mattress will fit. For example, never mind that a certain Queen bedframe measures an overall width of 96″—it’s still only going to accommodate a 60″ wide mattress!

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