ORDERS(7) BSD Miscellaneous Information Manual ORDERS(7)NAME
orders -- orders of magnitude
DESCRIPTION
The following table lists common multiples of bytes.
Name Prefix Power of 2 Power of 10
Kilobyte kB 2^10 10^3
Megabyte MB 2^20 10^6
Gigabyte GB 2^30 10^9
Terabyte TB 2^40 10^12
Petabyte PB 2^50 10^15
Exabyte EB 2^60 10^18
Zettabyte ZB 2^70 10^21
Yottabyte YB 2^80 10^24
The following table lists common bit rates as a power of ten.
Name Prefix Bit per second Byte per second
Bit per second bit/s 1 0.125
Byte per second B/s 8 1
Kilobit per second kbit/s 10^3 125
Kilobyte per second kB/s 8 * 10^3 1000
Megabit per second Mbit/s 10^6 125000
Megabyte per second MB/s 8 * 10^6 1000000
Gigabit per second Gbit/s 10^9 125000000
Gigabyte per second GB/s 8 * 10^9 1000000000
Terabit per second Tbit/s 10^12 125000000000
Terabyte per second TB/s 8 * 10^12 1000000000000
The following table lists common orders of magnitude as a power of ten.
Name Order Prefix Symbol Decimal
Septillionth 10^-24 yocto y 0.000000000000000000000001
Sextillionth 10^-21 zepto z 0.000000000000000000001
Quintillionth 10^-18 atto a 0.000000000000000001
Quadrillionth 10^-15 femto f 0.000000000000001
Trillionth 10^-12 pico p 0.000000000001
Billionth 10^-9 nano n 0.000000001
Millionth 10^-6 micro mu 0.000001
Thousandth 10^-3 milli m 0.001
Hundredth 10^-2 centi c 0.01
Tenth 10^-1 deci d 0.1
One 10^0 - - 1
Ten 10^1 deca da 10
Hundred 10^2 hecto h 100
Thousand 10^3 kilo k 1000
Million 10^6 mega M 1000000
Billion 10^9 giga G 1000000000
Trillion 10^12 tera T 1000000000000
Quadrillion 10^15 peta P 1000000000000000
Quintillion 10^18 exa E 1000000000000000000
Sextillion 10^21 zetta Z 1000000000000000000000
Septillion 10^24 yotta Y 1000000000000000000000000
SEE ALSO units(1), strsuftoll(3), number(6)STANDARDS
There have been various attempts to standardize the set of binary prefixes. Organizations such as International Electrotechnical Commission
(IEC) have proposed new prefixes such as ``kibi'', ``mebi'', ``gibi'', and ``yobi'', but the adoption has been slow at best.
BSD August 6, 2011 BSD
Check Out this Related Man Page
UNITS(7) Linux Programmer's Manual UNITS(7)NAME
units, kilo, kibi, mega, mebi, giga, gibi - decimal and binary prefixes
DESCRIPTION
Decimal prefixes
The SI system of units uses prefixes that indicate powers of ten. A kilometer is 1000 meter, and a megawatt is 1000000 watt. Below the
standard prefixes.
Prefix Name Value
y yocto 10^-24 = 0.000000000000000000000001
z zepto 10^-21 = 0.000000000000000000001
a atto 10^-18 = 0.000000000000000001
f femto 10^-15 = 0.000000000000001
p pico 10^-12 = 0.000000000001
n nano 10^-9 = 0.000000001
u micro 10^-6 = 0.000001
m milli 10^-3 = 0.001
c centi 10^-2 = 0.01
d deci 10^-1 = 0.1
da deka 10^ 1 = 10
h hecto 10^ 2 = 100
k kilo 10^ 3 = 1000
M mega 10^ 6 = 1000000
G giga 10^ 9 = 1000000000
T tera 10^12 = 1000000000000
P peta 10^15 = 1000000000000000
E exa 10^18 = 1000000000000000000
Z zetta 10^21 = 1000000000000000000000
Y yotta 10^24 = 1000000000000000000000000
The symbol for micro is the Greek letter mu, often written u in an ASCII context where this Greek letter is not available. See also
http://physics.nist.gov/cuu/Units/prefixes.html
Binary prefixes
The binary prefixes resemble the decimal ones, but have an additional 'i' (and "Ki" starts with a capital 'K'). The names are formed by
taking the first syllable of the names of the decimal prefix with roughly the same size, followed by "bi" for "binary".
Prefix Name Value
Ki kibi 2^10 = 1024
Mi mebi 2^20 = 1048576
Gi gibi 2^30 = 1073741824
Ti tebi 2^40 = 1099511627776
Pi pebi 2^50 = 1125899906842624
Ei exbi 2^60 = 1152921504606846976
See also
http://physics.nist.gov/cuu/Units/binary.html
Discussion
Before these binary prefixes were introduced, it was fairly common to use k=1000 and K=1024, just like b=bit, B=byte. Unfortunately, the M
is capital already, and cannot be capitalized to indicate binary-ness.
At first that didn't matter too much, since memory modules and disks came in sizes that were powers of two, so everyone knew that in such
contexts "kilobyte" and "megabyte" meant 1024 and 1048576 bytes, respectively. What originally was a sloppy use of the prefixes "kilo" and
"mega" started to become regarded as the "real true meaning" when computers were involved. But then disk technology changed, and disk
sizes became arbitrary numbers. After a period of uncertainty all disk manufacturers settled on the standard, namely k=1000, M=1000k,
G=1000M.
The situation was messy: in the 14k4 modems, k=1000; in the 1.44MB diskettes, M=1024000; etc. In 1998 the IEC approved the standard that
defines the binary prefixes given above, enabling people to be precise and unambiguous.
Thus, today, MB = 1000000B and MiB = 1048576B.
In the free software world programs are slowly being changed to conform. When the Linux kernel boots and says
hda: 120064896 sectors (61473 MB) w/2048KiB Cache
the MB are megabytes and the KiB are kibibytes.
Linux 2001-12-22 UNITS(7)