Data units

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Confused about kilo vs kibi ? Or b vs B? Learn about units on wikipedia and this NIST site.

IEC/SI-Units	bits		Bytes       Meaning/purpose
============	==========      ==========  ===================================== 
kb		1000		125         thousand bits (kilo bits)
Kib		1024		128         2^10 bits (Kilo bits or Kibi bits)
kB		8000		1000        thousand Bytes (kilo Bytes)
KiB		8192		1024        2^10 Bytes (Kilo Bytes or Kibi Bytes)
Mb		1000000		125000      million bits (mega bits)
Mib		1048576		131072      2^20 bits (Mega bits or Mebi bits)
MB		8000000		1000000     million Bytes (mega Bytes)
MiB		8388608		1048576     2^20 Bytes (Mega Bytes or Mebi Bytes)
Gb		1000000000	125000000   billion bits (giga bits)
Gib		1073741824	134217728   2^30 bits (Giga bits or Gibi bits)
GB		8000000000	1000000000  billion Bytes (giga Bytes)
GiB		8589934592	1073741824  2^30 Bytes (Giga Bytes or Gibi Bytes)
and so on ...

There is a big difference between b for bits and B for Bytes -- by a factor of 8 (since there's 8 bits in 1 byte). For a while, k and K were used interchangeably to mean 1024. Technically, it should have been the lower case; it is not a proper noun. It could have meant 1000 because kilo means 1000. Hence the KiloBinary ("kibi") unit was introduced to give "kilo" prefix its proper 10^3 meaning.

Storage devices like hard drives as well as communications speeds (like modem, ADSL, cable, Ethernet, etc) usually use units like kb, Mb, kB or MB.

Note: You should always use the correct unit and capitalisation to minimize confusion.

Speed vs. Amount of data[edit]

Internet transfer speeds are commonly denoted in bits and powers of 10 per second. E.g. 0.1Mb/s = 100kbps = 100kb/s = 12,5kB/s = 100 kilobits per second.

However, Vuze defaults to KibiBytes per second, this behavior can be changed under Options > Interface > Display options .

Powers of 2 are mostly used for data storage (e.g. filesizes, free space on a hard drive, amount of transfered data etc.). People often mean the file is 15MiB big if they say it's 15MB in size. Amounts of data are almost always noted in bytes, not in bits, thus you should use a capital B for sizes.


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