MB is the abbreviation for Megabytes. In data communication, a megabyte is 1 million bytes (1,048,576 bytes to be exact). A byte is a group of eight binary digits processed as a unit by a computer and used especially to represent an alphanumeric character. Megabytes (MB) are commonly associated with the diskspace of a website. Back to up

A unit of measure for computer memory or storage equivalent to approximately one million (1,048,576) bytes.

the unit for storage devices. On a HDD 1 MB = 1048576 bytes and on a card 1 MB = 1 million bytes. This is due to the manufacturers idea on good marketing.