Megabyte

This article is about a unit of data. For the ReBoot character, see Megabyte (ReBoot).

Multiple-byte units
Decimal Value Metric 1000 103 kB kilobyte 10002 106 MB megabyte 10003 109 GB gigabyte 10004 1012 TB terabyte 10005 1015 PB petabyte 10006 1018 EB exabyte 10007 1021 ZB zettabyte 10008 1024 YB yottabyte 10009 1027 RB ronnabyte 100010 1030 QB quettabyte	Binary Value IEC Memory 1024 210 KiB kibibyte KB kilobyte 10242 220 MiB mebibyte MB megabyte 10243 230 GiB gibibyte GB gigabyte 10244 240 TiB tebibyte TB terabyte 10245 250 PiB pebibyte – 10246 260 EiB exbibyte – 10247 270 ZiB zebibyte – 10248 280 YiB yobibyte – 10249 290 – – 102410 2100 – –
Orders of magnitude of data

A megabyte is a unit of information or computer storage equal to either 10⁶ (1,000,000) bytes or 2²⁰ (1,048,576) bytes, depending on context. In rare cases, it is used to mean 1000×1024 (1,024,000) bytes. It is commonly abbreviated as Mbyte or MB (compare Mb, for the megabit). The term megabyte was coined in 1970.

Definition

The term "megabyte" is ambiguous because it is commonly used to mean either 1000² bytes or 1024² bytes. The confusion originated as 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) is roughly equal to 1000 (10³), roughly corresponding SI multiples began to be used as approximate binary multiples. By the end of 2007, standards and government authorities including IEC, IEEE, EU, and NIST, had addressed this ambiguity by promulgating standards requiring the use of megabyte to describe strictly 1000² bytes and "mebibyte" to describe 1024² bytes. This is reflected in an increasing number of software projects, but most file managers still show file sizes in "megabytes" ("MB") in the binary sense (1024² bytes). The term remains ambiguous and it can follow any one of the following common definitions:

1. 1,000,000 bytes (1000², 10⁶): This is the definition recommended by the International System of Units (SI) and the International Electrotechnical Commission IEC. This definition is used in networking contexts and most storage media, particularly hard drives, Flash-based storage, and DVDs, and is also consistent with the other uses of the SI prefix in computing, such as CPU clock speeds or measures of performance.
2. 1,048,576 bytes (1024², 2²⁰): This definition is most commonly used in reference to computer memory, but most software that display file size or drive capacity, including file managers also use this definition. See Consumer confusion (in the "gigabyte" article).
3. 1,024,000 bytes (1000×1024): This is used to describe the formatted capacity of USB flash drives and the "1.44 MB" 3.5 inch HD floppy disk, which actually has a 1,440 KiB capacity, that is, 1,440×1,024 bytes, or 1,474,560 bytes.

Megabyte examples

1.44 MB floppy disks can store 1,474,560 bytes of data. MB in this context means 1,000 times 1,024 bytes.

Depending on compression methods and file format, a megabyte of data can roughly be:

• a 1024×1024 pixel bitmap image with 256 colors (8 bpp color depth).
• 1 minute of 128 kbit/s MP3 compressed music.
• 6 seconds of uncompressed CD audio.
• a typical book volume in text format (500 pages × 2000 characters).

See also

• binary prefix
• kilobyte
• gigabyte
• mebibyte
• megabit
• orders of magnitude (data)

External links

• 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 definitions
• IEC prefixes and symbols for binary multiples