The SI prefixes are defined as follows:
Factor  Symbol  Prefix  Prefix  Symbol  Factor  
10^{1}  d  deci  deca  da  10  
10^{2}  c  centi  hecto  h  10^{2}  
10^{3}  m  milli  kilo  k  10^{3}  
10^{6}  μ  micro  mega  M  10^{6}  
10^{9}  n  nano  giga  G  10^{9}  
10^{12}  p  pico  tera  T  10^{12}  
10^{15}  f  femto  peta  P  10^{15}  
10^{18}  a  atto  exa  E  10^{18}  
10^{21}  z  zepto  zetta  Z  10^{21}  
10^{24}  y  yocto  yotta  Y  10^{24} 
The above SI prefixes can be applied to all SI units, except those associated with computer binary data. For example:

Old Definitions:
 1 kb = (2^{10}) bits = 1,024 bits
 1 MB = (2^{10})^{2} Bytes = 1,048,576 Bytes
To make the SI prefixes universal and to avoid confusion in the future, International Electrotechnical Commission (IEC), the leading international organization for worldwide standardization in electrotechnology, approved in December 1998 standard names and symbols of prefixes for binary multiples to be used in the fields of data processing and transmission. The prefixes are:
Name  Prefix  Symbol  Factor 
kilobinary  kibi  Ki  2^{10} 
megabinary  mebi  Mi  (2^{10})^{2} 
gigabinary  gibi  Gi  (2^{10})^{3} 
terabinary  tebi  Ti  (2^{10})^{4} 
petabinary  pebi  Pi  (2^{10})^{5} 
exabinary  exbi  Ei  (2^{10})^{6} 
Based on the new definitions, the SI prefixes, k, M, and G, are back to their original meaning of 1,000, 1,000,000, and 1,000,000,000, respectively. The commonly known binary prefixes are written as Ki, Mi, and Gi and pronounced as kibi, mebi, and gibi, respectively.

New Definitions: (See the unit conversion calculator for more binary data units.)
 1 kilobit = 1 kb = 10^{3} bits = 1,000 bits
 1 kilobinarybit = 1 kibibit = 1 Kib = (2^{10}) bits = 1,024 bits
 1 megabyte = 1 MB = 10^{6} Bytes = 1,000,000 Bytes
 1 megabinarybyte = 1 mebibyte = 1 MiB = (2^{10})^{2} Bytes = 1,048,576 Bytes
The IEEE Standards Board decided that IEEE standards will be using the conventional, internationally adopted, definitions of the baseten SI prefixes, except that the basetwo definition may be used if such usage is explicitly pointed out on a casebycase basis.
List Units: A B C D EF G HI JL M N OP QR S T UZ 