It’s simple: the size. Standard Kings measure 76 inches wide and 80 inches long. California King beds measure 72 inches wide by 84 inches long. Cal King mattresses are 4 inches narrower and 4 inches longer than standard King mattresses. You typically can't interchangeably use the same bed frame or sheets for both bed sizes.

 

No. Twin beds measure 38” by 75”. Combining two would be significantly wider than a standard Full. Two Twin size mattresses are the width of a king mattress, though still 5 inches shorter. Two Twin XL mattresses, however, would be the same length and width as a King size mattress.

 

Yes. The terms Full bed and Double bed are used interchangeably to describe mattresses that measure 54 inches wide and 75 inches long.

 

It really depends on the size of your sleeping space and personal preferences. If you’re a single adult, a Full bed would be a space saver compared to a Queen bed and could be sufficient. However, for couples, a Queen bed is often recommended. Single sleepers who prefer having more floor space over sleeping space may want to consider a Twin mattress (or, for tall people, a Twin XL mattress) though for many they may not provide enough width.

 

Again, it depends on the space and your needs. Full size beds are commonly used in guest rooms as they take up little space and can accommodate two sleepers in a pinch. If you have the space though, we’d recommend going for a larger mattress, like a Queen size bed, for your guest room.

 

Length and width are not typically indicators of how thick a mattress will be. Mattress thickness is usually determined by the materials used to make the mattress, and whether it is a pillow top mattress, as the plush top will generally give it a taller profile by a couple of inches. Different mattress constructions can sometimes differ in height - for example, solid memory foam mattresses sometimes aren't as tall as innerspring mattresses.