The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (106) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities. However, in the computer and information technology fields, several other definitions are used that arose for historical reasons of convenience. A common usage has been to designate one megabyte as 1048576bytes (220 B), a measurement that conveniently expresses the binary multiples inherent in digital computer memory architectures. However, most standards bodies have deprecated this usage in favor of a set of binary prefixes, in which this quantity is designated by the unit mebibyte (MiB). Less common is a convention that used the megabyte to mean 1000×1024 (1024000) bytes.
1 Definitions 2 Examples of use 3 See also 4 References 5 External links
The megabyte is commonly used to measure either 10002 bytes or 10242
bytes. The interpretation of using base 1024 originated as a
compromise technical jargon for the byte multiples that needed to be
expressed by the powers of 2 but lacked a convenient name. As 1024
(210) approximates 1000 (103), roughly corresponding to the SI prefix
kilo-, it was a convenient term to denote the binary multiple. In 1998
International Electrotechnical Commission
1 MB = 1000000 bytes (= 10002 B = 106 B) is the definition recommended
International System of Units
In this convention, one thousand megabytes (1000 MB) is equal to one gigabyte (1 GB), where 1 GB is one billion bytes.
Main article: mebibyte
1 MB = 1048576 bytes (= 10242 B = 220 B) is the definition used by
In this convention, one thousand and twenty-four megabytes (1024 MB) is equal to one gigabyte (1 GB), where 1 GB is 10243 bytes.
Mixed 1 MB = 1024000 bytes (= 1000×1024 B) is the definition used to describe the formatted capacity of the 1.44 MB 3.5-inch HD floppy disk, which actually has a capacity of 1474560bytes.
Semiconductor memory doubles in size for each address lane added to an integrated circuit package, which favors counts that are powers of two. The capacity of a disk drive is the product of the sector size, number of sectors per track, number of tracks per side, and the number of disk platters in the drive. Changes in any of these factors would not usually double the size. Sector sizes were set as powers of two (most common 512 bytes or 4096 bytes) for convenience in processing. It was a natural extension to give the capacity of a disk drive in multiples of the sector size, giving a mix of decimal and binary multiples when expressing total disk capacity. Examples of use
1.44 MB floppy disks can store 1,474,560 bytes of data. MB in this context means 1,000×1,024 bytes.
Depending on compression methods and file format, a megabyte of data can roughly be:
a 1 megapixel bitmap image with 256 colors (8 bits/pixel color depth)
stored without any compression.
a 4 megapixel
The human genome consists of DNA representing 800 MB of data. The parts that differentiate one person from another can be compressed to 4 MB. See also
Timeline of binary prefixes
^ "Archived copy". Archived from the original on June 7, 2007.
Retrieved June 1, 2007.
^ a b c "Definitions of the SI units: The binary prefixes". National
Institute of Standards and Technology.
^ SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1
gigabyte (GB) = 1 billion bytes."
Mac OS X
Historical Notes About The Cost Of Hard Drive Storage Space
the megabyte (established definition in Networking and Storage
industries; from whatis.com)
International Electrotechnical Commission
v t e
Units of information
nibble byte syllable parcel word
unibit (1) dibit (2) tribit (3) quadbit (4)
quartet (4) sextet (6) octet (8) hextet (16)
declet (10) doublet (16) quadlet (32) octlet (64) hexlet (128)
triad (3) tetrad (4) pentad (5) hexad (6) heptad (7) octad (8)
slab (12) catena (24)
Traditional bit units
kilobit megabit gigabit terabit petabit exabit zettabit yottabit
Traditional byte units
kilobyte megabyte gigabyte terabyte petabyte exabyte zettabyte yottabyte
IEC bit units
kibibit mebibit gibibit tebibit pebibit exbibit zebibit yobibit
IEC byte units
kibibyte mebibyte gibibyte tebibyte pebibyte exbibyte