Choosing the best mattress for a particular size of room depends on the room dimensions, other furniture sharing the room, the size and number of the intended users and personal space preferences. The available mattress sizes depend on geography, since the dimensions and names vary by country, according to Wikipedia.
In the United States, the standard available mattress sizes in order of increasing size are crib, twin or single, twin XL, full or double, queen, king or Eastern king, and California king or Western king, according to the Better Sleep Council. As of January 2015, the queen mattress is the most popular size in the United States. The typical dimensions of a queen are 60 inches wide by about 80 inches long. Queens are a recommended choice for guest rooms and smaller master bedrooms, as well as for couples who do not mind sharing sleeping space.
To adequately accommodate a queen mattress with a minimum amount of space to move around in, the bedroom should measure at least 10 feet by 10 feet, recommends SFGate Home Guides. Bedrooms that are 16 inches wider can accommodate the standard king, which is known also as the Eastern king. The larger size provides the equivalent amount of personal sleeping space for two people as does two twin mattresses, notes About.com.