The sizes of normal beds and their accompanying mattress dimensions in developed countries around the world are usually standard, but include some important minor differences. Whether one is custom building furniture, or just shopping for linens, it is very important to know the exact measurements of the mattress that will be slept on. In the North America, mattresses are, as a general rule, wider than their counterparts in other parts of the world. However, with the exception of mattresses used in the United Kingdom and Australia, mattresses in the rest of the world tend to be slightly longer than our mattresses. An important exception to the "wider in the US" rule is the size of beds in hotels. Many hotels offer rooms with beds they call "King Size" but which are significantly narrower to individuals accustomed to sleeping in a "Standard King." More detailed charts can be found here.
Information about mattress constructions types can be found here.