Megabit
Encyclopedia
The megabit is a multiple of the unit bit
for digital information
or computer storage
. The prefix mega (symbol M) is defined in the International System of Units
(SI) as a multiplier of 106 (1 million), and therefore
The megabit has the unit symbol Mbit or Mb.
Using the common byte
size of 8 bits, 1 Mbit is roughly equal to 125 kilobyte
s (kB) or approximately 122 kibibyte
s (KiB).
The megabit is closely related to the mebibit
, a unit multiple derived from the binary prefix
mebi (symbol Mi) of the same order of magnitude, which is equal to = , or approximately 5% larger than the megabit. Despite the definitions of these new prefixes for binary-based quantities of storage by international standards organizations, memory semiconductor chips are still marketed using the metric prefix names to designate binary multiples.
The megabit is widely used when referring to data transfer rates of computer networks or telecommunications systems. Network transfer rates and download speeds often use the megabit as the amount transferred per time unit, e.g., a 100 Mbit/s (megabit per second) Fast-Ethernet
connection, or a 10 Mbit/s Internet access service, whereas the sizes of data units (files) transferred over these networks are often measured in megabytes. To achieve a transfer rate of one megabyte per second one needs a network connection with a transfer rate of eight megabits per second. This can be confusing for internet users assuming the values are in kilobytes and megabytes per second. If one goes to buy a 2 megabit per second internet plan, they are really only getting a 250 kilobyte per second plan.
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
for digital information
Information
Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...
or computer storage
Computer storage
Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
. The prefix mega (symbol M) is defined in the International System of Units
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
(SI) as a multiplier of 106 (1 million), and therefore
- 1 megabit = = = 1000 kilobitKilobitThe kilobit is a multiple of the unit bit for digital information or computer storage. The prefix kilo is defined in the International System of Units as a multiplier of 103 , and therefore,...
s.
The megabit has the unit symbol Mbit or Mb.
Using the common byte
Byte
The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...
size of 8 bits, 1 Mbit is roughly equal to 125 kilobyte
Kilobyte
The kilobyte is a multiple of the unit byte for digital information. Although the prefix kilo- means 1000, the term kilobyte and symbol KB have historically been used to refer to either 1024 bytes or 1000 bytes, dependent upon context, in the fields of computer science and information...
s (kB) or approximately 122 kibibyte
Kibibyte
The kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 1024; therefore, 1 kibibyte is . The unit symbol for the kibibyte is KiB. The unit was established by the International Electrotechnical Commission in 1999 and has been accepted for use...
s (KiB).
The megabit is closely related to the mebibit
Mebibit
The mebibit is a multiple of the bit, a unit of digital information storage, prefixed by the standards-based multiplier mebi , a binary prefix meaning 220...
, a unit multiple derived from the binary prefix
Binary prefix
In computing, a binary prefix is a specifier or mnemonic that is prepended to the units of digital information, the bit and the byte, to indicate multiplication by a power of 2...
mebi (symbol Mi) of the same order of magnitude, which is equal to = , or approximately 5% larger than the megabit. Despite the definitions of these new prefixes for binary-based quantities of storage by international standards organizations, memory semiconductor chips are still marketed using the metric prefix names to designate binary multiples.
The megabit is widely used when referring to data transfer rates of computer networks or telecommunications systems. Network transfer rates and download speeds often use the megabit as the amount transferred per time unit, e.g., a 100 Mbit/s (megabit per second) Fast-Ethernet
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
connection, or a 10 Mbit/s Internet access service, whereas the sizes of data units (files) transferred over these networks are often measured in megabytes. To achieve a transfer rate of one megabyte per second one needs a network connection with a transfer rate of eight megabits per second. This can be confusing for internet users assuming the values are in kilobytes and megabytes per second. If one goes to buy a 2 megabit per second internet plan, they are really only getting a 250 kilobyte per second plan.
Usage conventions
- In Telecommunications, use of the correct SI definition of the unit is standard.
- Standard industry practice in RAMRam-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
and ROMRead-only memoryRead-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
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 512 Mb invariably contains 229 bits = = 512 Mibit of storage, or , variously referred to as either 64 mebibyteMebibyteThe mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...
s or 64 (binary) megabyteMegabyteThe megabyte is a multiple of the unit byte for digital information storage or transmission with two different values depending on context: bytes generally for computer memory; and one million bytes generally for computer storage. The IEEE Standards Board has decided that "Mega will mean 1 000...
s. - 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 mebibitMebibitThe mebibit is a multiple of the bit, a unit of digital information storage, prefixed by the standards-based multiplier mebi , a binary prefix meaning 220...
(Mibit). The vast majority of SNESSuper Nintendo Entertainment SystemThe Super Nintendo Entertainment System is a 16-bit video game console that was released by Nintendo in North America, Europe, Australasia , and South America between 1990 and 1993. In Japan and Southeast Asia, the system is called the , or SFC for short...
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 to a 1 byte. Therefore, a 4 megabit cartridge had a capacity of 512 KiBKibibyteThe kibibyte is a multiple of the unit byte for quantities of digital information. The binary prefix kibi means 1024; therefore, 1 kibibyte is . The unit symbol for the kibibyte is KiB. The unit was established by the International Electrotechnical Commission in 1999 and has been accepted for use...
, and a 8 megabit cartridge held 1 MiBMebibyteThe mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 220, therefore 1 mebibyte is . The unit symbol for the mebibyte is MiB. The unit was established by the International Electrotechnical Commission in 2000 and has been accepted for use by all major...
of data.