megabit

A megabit is an SI-multiple (see prefix mega) of the unit of bit for digital information storage or transmission. The International Electrotechnical Commission's standard IEC 60027 specifies the symbol to be Mbit, but Mb is also in common use.

1 megabit = 1000² bits = 10⁶ bits = 1000000bits.

Based on an eight-bit-sized byte this is equal to 125000bytes, 125 kilobytes (kB), or approximately 122 kibibytes (KiB).

The megabit is commonly used when referring to data transfer rates of computer networks or telecommunications systems, e.g., a 100 Mbit/s (megabit per second) Fast-Ethernet connection, or a 10 Mbit/s Internet access service.

The binary-interpreted counterpart of the megabit, the mebibit (Mibit), refers to the quantity of 1024² bits = 1048576bits.

Usage conventions

• In Telecommunications, use of the correct SI definition of the unit is standard.
• Standard industry practice in RAM and ROM manufacture has been to use the Mb abbreviation in reference to the binary interpretation of the megabit. For example, a single discrete DDR3 chip specified at 512Mb invariably contains 2²⁹ bits = 536870912bits = 512 Mibit of storage,^[1] or 671088648-bit bytes, variously referred to as either 64 mebibytes or 64 (binary) megabytes.
• During the 16-bit game console era, the megabit was a commonly-used measure of the size (computer data storage capacity) of game cartridges. This size represented one mebibit (Mibit). The vast majority of SNES and Mega Drive (Genesis) games were produced on 8 megabit cartridges, although other sizes, such as 4, 12, 16, 24, 32, and 48 megabit cartridges appeared. The standard rule is: 8 bits = 1 byte. Therefore a 4 megabit cartridge had a capacity of 512 KiB, an 8 megabit cartridge held 1 MiB of data.

See also

• Megabyte
• Orders of magnitude (data)

References