Mattresses are measured in inches in the United States and are classified by size according to width and length. Japan, continental Europe, Australia and Latin America measure mattress size in centimeters, according to SleepoPedia.com.
In the United Kingdom and Ireland, a queen-size mattress is referred to as a king mattress, says SleepoPedia.com. Some bed frames, such as European or antique styles, require specialty sized mattress sets, according to The Bedding Experts. Most mattresses are commonly 75 or 80 inches long in the United States. Widths vary widely and range from 30 to 76 inches, dependent on the size of mattress desired, according to The Bedding Experts mattress sizing charts.