A measurement of storage capacity equal to approximately 1 million bytes (1,048,576 bytes). A typical IBM compatible floppy disk holds about 1.44 MB of data. A typical CD-ROM holds over 600 MB of data. A 1 MB file takes about 10 minutes to download at 28,800bps. Don't know your KB from your MB? Try our memory and storage converter. (Also see powers of ten, kilobyte, gigabyte, terabyte, exabyte, petabyte, zettabyte and yottabyte.) A MB is 1,000 KB. When used to describe data storage, 1,048,576 (2 to the 20th power) bytes. Megabyte is frequently abbreviated as M as well as MB. When used to describe data transfer rates (speed of data flow), as in MBps (megabytes per second), it refers to one million bytes.