Shopping for a new mattress? Then it's important to make sure that you buy the right size. And this can get a bit complicated. Because like clothes and shoes, standard mattress sizes often vary wildly across national boundaries.
Just like how "size 10 shoes" are different in the US, UK and EU, what "king-sized mattress" means in America isn't the same if you're on the other side of the Atlantic. So even if you think you've found the best mattress, once it's delivered it may prove to be the wrong size for your needs.
That's said, if you've spotted a bargain in the mattress sales – and there are some great Black Friday mattress deals to be had this year – you want to act fast, and don't want to waste lots of time doing research. So to help you out, we answer all your questions below on how big a king size mattress is, and the different king options on offer in the US and UK.
What are the dimensions of a king size bed?
In the US, a king size bed is 76 inches wide and 80 inches long (or 193cm wide and 203cm long). In the UK, a king size bed is 60 inches wide and 79 inches long (or 150cm wide and 200cm long).
| Name | US (imperial) | US (metric) | UK (imperial) | UK (metric) |
|---|---|---|---|---|
| King | 76 x 80" | 193 x 203cm | 60 x 79" | 150 x 200cm |
| Super king | N/A | N/A | 71 x 79" | 180 x 200cm |
| Cal king | 72 x 84" | 183 x 213cm | N/A | N/A |
| Split king | 76 x 80" | 193 x 203cm | N/A | N/A |
| Split CA king | 72 x 84" | 183 x 213cm | N/A | N/A |
What size is a king size bed in the US?
A US king size bed is 76 inches wide and 80 inches long (that's approximately 193cm wide and 203cm long). It's one of the bigger two-person sleeping options, so it's a good choice for couples who are larger in size, like to spread out, or routinely have a child or pet joining them in bed.
US queen vs king size bed
If you're tight on space, the next size down from a US king size bed (76 x 80 inches / 193 x 203cm) is a US queen (60 x 80 inches / 152 x 203cm). A US queen size bed is also designed for two people, and it's the same length, but 16 inches (approximately 61cm) narrower. A queen is perhaps the most popular bed size for couples and while smaller, is plenty big enough for many couples.
There's one smaller couples' bed size: a full, which is 54 inches wide and 75 inches long (approximately 137 x 191cm). If a king size feels like it might be too small, meanwhile, the next size up is a California king, which we'll cover below.
Alternatively, if motion transfer is an issue for you, you could try a split king. This has the same dimensions as a US king, but split over two, equally-sized mattresses, which sit next to each other in the same bed.
A split king might sound weird, but they're popular with couples who have very different sleeping patterns, and/or sleeping times (such is if one is a shift worker). Because each mattress is distinct, it means that one person moving around will bother the other person less. On the downside, the gap between the mattress may cause discomfort if one or both of you rolls into the middle. Also note you'll need specialised bed sheets.
US king vs UK king
While you might expect 'king' to mean the same thing in both the US and the UK, they actually have different dimensions, depending which side of the Atlantic you reside. In terms of width, they're pretty similar: the UK king is just one inch narrower at 79 inches (200cm) to the 80 inches (203cm) width of the US king. Where the two versions really differ, though, is in length. The US king is 76 inches (193cm) long while the UK king is more than 20 per cent shorter, at just 60 inches (150cm) long.
What size is a king size bed in the UK?
A UK king size bed is shorter than a US king (see above). A UK king is 60 inches wide and 79 inches long (or 150cm wide and 200cm long). That makes it a significant step up in size from a UK double bed size, which is 53 x 75 inches (or 135cm x 190cm), making it a great choice for couples who like to spread out and have a lot of room in bed, especially if you often invite children or pets to come on board.
If you want even more space, the next size up is a UK super king, which measures 71 x 79 inches (or 180cm x 200cm). However, you'll need a pretty huge room to accommodate a bed that size, and so for most couples, a king will hit the sweet spot between the room you have in bed, and the room you have around the bed.
What size is a super king size bed?
A super king is something you only find in the UK. It's the next step up in size from a UK king, and measures 71 x 79 inches (or 180cm x 200cm). That makes it 11 inches (30cm) wider but no longer than a UK king, which is 60 inches wide and 79 inches long (or 150cm wide and 200cm long). Its closest US equivalent is the California king, which is only a little bigger at 72 x 84 inches (or 183 x 213cm).
The super king is a good choice for couples with money to spend, who like to spread out on their bed, and who have a large room to place it in. Conversely, most couples with standard size bedrooms may find there isn't enough room for a super king, and a UK king size will be a more practical option.
While the super king is the largest of the UK standard sizes, that doesn't mean you can't buy bigger. Many brands and retailers sell beds that exceed its measurements, under names such as 'Caesar' or 'Emporer'. It's just that there's no agreed size or naming conventions for these bigger beds across the industry.
What size is a Cal king bed?
As you might expect from the name, the California king (aka Cal king, CA king or Western King) is only found in North America. The only way you'll see a bed with this monicker in the UK or Europe will be as an export.
A California king mattress is 72 x 84 inches (183 x 213cm), and is the same size as two twin XL mattresses put together, making it a good choice for couples. It's slightly narrower than a US King (at 72 inches to the latter's 76), but also longer (at 84 inches to the latter's 80), making it ideal for people over six feet tall.
If you and your partner sleep differently, or at different times of the night (eg shift working), you can get a split version of the California king. This has the same overall dimensions, but divided between two mattresses, each 36 inches (90cm) wide, which sit next to each other. This minimises motion transfer, although some may find the gap between the mattresses uncomfortable when lying across the middle of the bed.
The Golden State doesn't have the naming monopoly on outsized beds. There's also the Wyoming king, which is 84 by 84 inches (213 x 213cm). That makes it as long as the California king but an entire 12 inches (30cm) wider.
There's the Texas king, which is 80 by 98 inches (203 x 249cm), making it a popular choice among very tall people. And for the maximum sleeping real-estate, the Alaskan king measures a generous 108 by 108 inches (274 x 274cm); a good two feet longer than the California king.
Cal king vs king size mattress dimensions
A US king size bed is 76 inches wide and 80 inches long (that's approximately 193cm wide and 203cm long). A California king mattress is 72 x 84 inches (183 x 213cm), making it both four inches narrower and four inches longer than a US King. For this reason, it's good for couples where one or both partners is taller than average.
What size is a split king bed?
A split mattress is exactly what it sounds like. Rather than one, large mattress you get two, separate mattresses that sit next to each other on the bed. For example, a split king has the same total dimensions as a US king (76 x 80 inches) but is made up of two 38 x 80 inch mattress rather than one big one.
Similarly, a split Cal king has the same dimensions as a Cal king (72 x 84 inches) but is made up of two 36 x 84 inch mattresses rather than one big one.
Split mattresses are popular with couples where one of the partners tosses and turns a lot in the night. On a normal bed, that would cause motion transfer across the mattress, waking up the other partner. On a split mattress, however, they'll feel a lot less disturbing movement within the bed.
Split mattresses also work better where one partner prefers a softer mattress and the other a firmer one, as the two mattresses can be of different firmness levels. On the downside, split mattresses require specialised sheets, and the gap in between the mattresses can be uncomfortable if you roll into it.
Queen vs king size bed
Queen and king sizes are different in the US and UK, so it's always worth checking which one a retailer is talking about.
In the US, a queen size bed is 60 inches wide and 80 inches long (or 152cm wideand 203cm long). In the UK, a queen size bed is the same as a small double, making it 48 inches wide and 75 inches long (or 120cm wide and 190cm long).
In the US, a king size bed is 76 inches wide and 80 inches long (or 193cm wide and 203cm long). In the UK, a king size bed is 60 inches wide and 79 inches long (or 150cm wide and 200cm long).
Read more:
- How big is a single mattress?
- How big is a twin size bed?
- RV mattress size chart: your guide to the different beds available
