Mattress sizes vary depending on the country and the degree of ornamentation of the bed frame. Most mattress brands offer six standard sizes: twin, twin XL, full, queen, king, and California king. The most common mattress sizes in the US are twin, full, queen, and king. Here are the dimensions of the six standard mattress sizes:

• Twin: 38 inches wide by 75 inches long
• Twin XL: 38 inches wide by 80 inches long
• Full: 54 inches wide by 75 inches long
• Queen: 60 inches wide by 80 inches long
• King: 76 inches wide by 80 inches long
• California King: 72 inches wide by 84 inches long

There are also non-standard variations and oversized mattresses available. The choice of size should depend on your space, sleeping preferences, and the number of sleepers.