Megabyte

<h2 id="definitions">Definitions</h2>
<p>The unit megabyte is commonly used for 10002 (one million) bytes or 10242 bytes. The interpretation of using base 1024 originated as technical jargon for the byte <a href="/facts/SI_prefix/Y2MzkaeL">multiples</a> 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 <a href="/facts/Kilo-/akxTdXyp">kilo-</a>, it was a convenient term to denote the binary multiple. In 1999, the <a href="/facts/International_Electrotechnical_Commission/hSK0kjwI">International Electrotechnical Commission</a> (IEC) published standards for <a href="/facts/Binary_prefix/oM3wgJgW">binary prefixes</a> requiring the use of <i>megabyte</i> to denote 10002 bytes, and <i><a href="/facts/Mebibyte/BNHUp9Qq">mebibyte</a></i> to denote 10242 bytes.  By the end of 2009, the IEC Standard had been adopted by the <a href="/facts/IEEE/UddC4pUW">IEEE</a>, <a href="/facts/European_Union/6GYcR8qM">EU</a>, <a href="/facts/ISO/IacYR7Yg">ISO</a> and <a href="/facts/NIST/gr9Fnh85">NIST</a>. Nevertheless, the term megabyte continues to be widely used with different meanings.
</p>
<h3>Base 10</h3>
1 MB = 1000000 bytes (= 10002 B = 106 B) is the definition following the rules of the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a> (SI), and the <a href="/facts/International_Electrotechnical_Commission/hSK0kjwI">International Electrotechnical Commission</a> (IEC).<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> This definition is used in <a href="/facts/Computer_network/3w5RM99p">computer networking</a> contexts and most <a href="/facts/Storage_media/uCvJ6nrq">storage media</a>, particularly <a href="/facts/Hard_drive/kekLSGSE">hard drives</a>, <a href="/facts/Flash_memory/Cn8JsStx">flash</a>-based storage,<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> and <a href="/facts/DVD/7fJsHJrN">DVDs</a>, and is also consistent with the other uses of the <a href="/facts/SI_prefix/Y2MzkaeL">SI prefix</a> in computing, such as <a href="/facts/Megahertz/6Wshj5qm">CPU clock speeds</a> or <a href="/facts/FLOPS/6zYlH68F">measures of performance</a>. The <a href="/facts/Mac_OS_X/Y93vVpTm">Mac OS X</a> 10.6 file manager is a notable example of this usage in software. Since <a href="/facts/Mac_OS_X_Snow_Leopard/GGNogRTe">Snow Leopard</a>, file sizes are reported in decimal units.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a>
<p>In this convention, one thousand megabytes (1000 MB) is equal to one gigabyte (1 GB), where 1 GB is one billion bytes.
</p>
<h3>Base 2</h3>
<p class="note">Main article: <a href="/facts/Mebibyte/BNHUp9Qq">Mebibyte</a></p>
1 MB = 1048576 bytes (= 10242 B = 220 B) is the definition used by <a href="/facts/Microsoft_Windows/bwhAhuSL">Microsoft Windows</a> in reference to <a href="/facts/Computer_memory/hQKVQ51J">computer memory</a>, such as <a href="/facts/Random-access_memory/DuD4bxh6">random-access memory</a> (RAM). This definition is synonymous with the unambiguous binary unit <a href="/facts/Mebibyte/BNHUp9Qq">mebibyte</a>. In this convention, one thousand and twenty-four megabytes (1024 MB) is equal to one gigabyte (1 GB), where 1 GB is 10243 bytes (i.e., 1 <a href="/facts/Gibibyte/BNHUp9Qq">GiB</a>).
<h3>Mixed</h3>
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 <a href="/facts/Floppy_disk/rShxfuxa">floppy disk</a>, which actually has a capacity of 1474560bytes.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a>
<p>Randomly addressable 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.
</p>
<h2 id="examples-of-use">Examples of use</h2>

<p>Depending on compression methods and <a href="/facts/File_format/qrXbwJaH">file format</a>, a megabyte of data can roughly be:
</p>
<ul><li>a 1 <a href="/facts/Megapixel/UzwBvXBV">megapixel</a> <a href="/facts/Bitmap/Fr80ySnT">bitmap</a> image (e.g. ~<a href="/facts/XGA%2B/zyMA9HHI">1152 × 864</a>) with 256 colors (8 bits/pixel <a href="/facts/Color_depth/0X7zI9BP">color depth</a>) stored without any compression.</li>
<li>6 seconds of <a href="/facts/Compact_Disc_Digital_Audio/FDMqNLw5">44.1 kHz/16 bit</a> <a href="/facts/Audio_file_format/hLgkfATf">uncompressed</a> CD audio.</li>
<li>1 minute of 128 <a href="/facts/Kilobits_per_second/Nv9VoT7T">kbit/s</a> <a href="/facts/MP3/yrBpxUSD">MP3</a> <a href="/facts/Audio_file_format/hLgkfATf">lossy compressed</a> audio.</li>
<li>a typical English book volume in plain text format (500 pages × 2000 characters per page).</li></ul>
<p>The novel <i><a href="/facts/The_Picture_of_Dorian_Gray/fzKyrdJM">The Picture of Dorian Gray</a></i>, by <a href="/facts/Oscar_Wilde/fRCAnvGk">Oscar Wilde</a>, hosted on <a href="/facts/Project_Gutenberg/2l0R6GgQ">Project Gutenberg</a> as an uncompressed plain text file, is 0.429 MB. <i><a href="/facts/Great_Expectations/TEWCTaDy">Great Expectations</a></i> is 0.994 MB,<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> and <i><a href="/facts/Moby_Dick/lBQqePwN">Moby Dick</a></i> is 1.192 MB.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> 
The <a href="/facts/Human_genome/VTV85pbn">human genome</a> consists of DNA representing 800 MB of data. The parts that differentiate one person from another can be compressed to 4 MB.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a>
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Timeline_of_binary_prefixes/jxXUso6q">Timeline of binary prefixes</a></li>
<li><a href="/facts/Gigabyte/s2hb2SEg">Gigabyte § Consumer confusion</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="https://web.archive.org/web/20140728221058/http://ns1758.ca/winch/winchest.html">Historical Notes About The Cost Of Hard Drive Storage Space</a></li>
<li><a href="http://searchstorage.techtarget.com/sDefinition/0,,sid5_gci212542,00.html">the megabyte</a> (established definition in Networking and Storage industries; from <a href="http://whatis.techtarget.com/definition/0,,sid9_gci551931,00.html">whatis.com</a>)</li>
<li><a href="https://web.archive.org/web/20090403051731/http://www.iec.ch/zone/si/si_bytes.htm">International Electrotechnical Commission definitions</a></li>
<li><a href="http://members.optus.net/alexey/prefBin.xhtml">IEC prefixes and symbols for binary multiples</a> <a href="https://web.archive.org/web/20040615185053/http://members.optus.net/alexey/prefBin.xhtml">Archived</a> 2004-06-15 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"SI Prefixes". Bureau international des poids et mesures. Archived from the original on June 7, 2007. Retrieved June 1, 2007. <a href="https://web.archive.org/web/20070607000414/http://www.bipm.org/en/si/si_brochure/chapter3/prefixes.html" target="_blank">https://web.archive.org/web/20070607000414/http://www.bipm.org/en/si/si_brochure/chapter3/prefixes.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>"Definitions of the SI units: The binary prefixes". National Institute of Standards and Technology. <a href="http://physics.nist.gov/cuu/Units/binary.html" target="_blank">http://physics.nist.gov/cuu/Units/binary.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>"Definitions of the SI units: The binary prefixes". National Institute of Standards and Technology. <a href="http://physics.nist.gov/cuu/Units/binary.html" target="_blank">http://physics.nist.gov/cuu/Units/binary.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>SanDisk USB Flash Drive "Note: 1 megabyte (MB) = 1 million bytes; 1 gigabyte (GB) = 1 billion bytes." <a href="https://web.archive.org/web/20080513155718/http://apac.sandisk.com/Products/Catalog(1349)-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx" target="_blank">https://web.archive.org/web/20080513155718/http://apac.sandisk.com/Products/Catalog(1349)-SanDisk_Extreme_Ducati_Edition_USB_Flash_Drive.aspx</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>"How Mac OS X reports drive capacity". Apple Inc. 2009-08-27. Retrieved 2009-10-16. <a href="http://support.apple.com/kb/TS2419" target="_blank">http://support.apple.com/kb/TS2419</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
<li id="fn:6"><p>Tracing the History of the Computer - History of the Floppy Disk <a href="http://www.computernostalgia.net/articles/HistoryoftheFloppyDisk.htm" target="_blank">http://www.computernostalgia.net/articles/HistoryoftheFloppyDisk.htm</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li>
<li id="fn:7"><p>Dickens, Charles (July 1, 1998). Great Expectations – via Project Gutenberg. <a href="https://www.gutenberg.org/ebooks/1400" target="_blank">https://www.gutenberg.org/ebooks/1400</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li>
<li id="fn:8"><p>Melville, Herman (July 1, 2001). Moby Dick; Or, The Whale – via Project Gutenberg. <a href="https://www.gutenberg.org/ebooks/2701" target="_blank">https://www.gutenberg.org/ebooks/2701</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li>
<li id="fn:9"><p>Christley, S.; Lu, Y.; Li, C.; Xie, X. (2008). "Human genomes as email attachments". Bioinformatics. 25 (2): 274–275. doi:10.1093/bioinformatics/btn582. PMID 18996942. <a href="https://doi.org/10.1093%2Fbioinformatics%2Fbtn582" target="_blank">https://doi.org/10.1093%2Fbioinformatics%2Fbtn582</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li>
</ol>

Megabyte open-in-new

Megabyte