Formats
From the 1950s through to the 1980s, the 12" LP record and the 45 rpm record were the major formats for distribution of popular music, and the LP format is still used for occasional new releases, though it has largely been supplanted by other formats. The size of the typical cardboard LP sleeve cover is 12.375 in (31.43 cm) square.
Since the mid-1990s, the compact disc (CD) has become the most common form of physically distributed music products. Packaging formats vary, including the very common plastic jewel case, and the popular cardboard and plastic combination commonly known as a Digipak. Typically the album cover component of these packages is approximately 4.75 in (12.1 cm) square.
Read more about this topic: Album Cover