
 1st CGPM, 1889
Sanction of the international prototypes of the metre and the kilogram 
 3rd CGPM, 1901
Declaration concerning the definition of the litre 
 3rd CGPM, 1901
Declaration on the unit of mass and on the definition of weight; conventional value of g_{n} 
 7th CGPM, 1927
Definition of the metre by the international Prototype 
 CIPM, 1946
Definition of photometric units 
 CIPM, 1946
Definitions of electric units 
 9th CGPM, 1948
Triple point of water; thermodynamic scale with a single fixed point; unit of quantity of heat (joule) 
 CGPM, 1948
Adoption of "degree Celsius" 
 9th CGPM, 1948
Proposal for establishing a practical system of units of measurement 
 9th CGPM, 1948
Writing and printing of unit symbols and of numbers 
 10th CGPM, 1954
Definition of the thermodynamic temperature scale 
 10th CGPM, 1954
Definition of the standard atmosphere 
 10th CGPM, 1954
Practical system of units 
 CIPM, 1956
Definition of the unit of time (second) 
 CIPM, 1956
Système International d'Unités 
 11th CGPM, 1960
Definition of the metre 
 11th CGPM, 1960
Definition of the unit of time (second) 
 11th CGPM, 1960
Système International d'Unités 
 11th CGPM, 1960
Cubic decimetre and litre 
 CIPM, 1961
Cubic decimetre and litre 
 CIPM, 1964
Atomic and molecular frequency standards 
 12th CGPM, 1964
Atomic standard of frequency 
 12th CGPM, 1964
Litre 
 12th CGPM, 1964
Curie 
 12th CGPM, 1964
SI prefixes femto and atto 
 CIPM, 1967
Decimal multiples and submultiples of the unit of mass 
 13th CGPM, 1967/68
SI unit of time (second) 
 13th CGPM, 1967/68
SI unit of thermodynamic temperature (kelvin) 
 13th CGPM, 1967/68
Definition of the SI unit of thermodynamic temperature (kelvin) 
 13th CGPM, 1967/68
SI unit of luminous intensity (candela) 
 13th CGPM, 1967/68
SI derived units 
 13th CGPM, 1967/68
Abrogation of earlier decisions (micron, new candle) 
 CIPM, 1969
Système International d'Unités, Rules for application of Resolution 12 of the 11th CGPM (1960) 
 CCDS, 1970
Definition of TAI 
 CGPM, 1971
Pascal and siemens 
 14th CGPM, 1971
International Atomic Time, function of CIPM 
 14th CGPM, 1971
SI unit of amount of substance (mole) 
 15th CGPM, 1975
Recommended value for the speed of light 
 15th CGPM, 1975
Coordinated Universal Time (UTC) 
 15th CGPM, 1975
SI units for ionizing radiation: becquerel 
 15th CGPM, 1975
SI units for ionizing radiation: gray 
 15th CGPM, 1975
SI prefixes peta and exa 
 16th CGPM, 1979
SI unit of luminous intensity (candela) 
 16th CGPM, 1979
Special name for the SI unit of dose equivalent (sievert) 
 16th CGPM, 1979
Symbols for the litre 
 CIPM, 1980
SI supplementary units (radian and steradian) 
 17th CGPM, 1983
Definition of the metre 
 17th CGPM, 1983
On the realization of the definition of the metre 
 CIPM, 1984
Concerning the sievert 
 18th CGPM, 1987
Forthcoming adjustment to the representations of the volt and of the ohm 
 CIPM, 1988
Representation of the volt by means of the Josephson effect 
 CIPM, 1988
Representation of the ohm by means of the quantum Hall effect 
 CIPM, 1989
The International Temperature Scale of 1990 
 19th CGPM, 1991
SI prefixes zetta, zepto, yotta and yocto 
 20th CGPM, 1995
Elimination of the class of supplementary units in the SI 
 21st CGPM, 1999
The definition of the kilogram 
 21st CGPM, 1999
Special name for the SI derived unit mole per second, the katal, for the expression of catalytic activity 
 CIPM, 2000
"Use of the von Klitzing constant to express the value of a reference standard of resistance as a function of the quantum Hall effect" 
 CIPM, 2001
"SI units" and "units of the SI" 
 CIPM, 2002
Revision of the practical realization of the definition of the metre 
 CIPM, 2002
Dose equivalent 
 CIPM, 2003
Revision of the Mise en Pratique list of recommended radiations 
 22nd CGPM, 2003
Symbol for the decimal marker 
 CIPM, 2005
Clarification of the definition of the kelvin, unit of thermodynamic temperature 
 CIPM, 2005
Revision of the Mise en pratique list of recommended radiations 
 CIPM, 2006
Concerning secondary representations of the second 
 CIPM, 2007
Revision of the Mise en pratique list of recommended radiations 
 23rd CGPM, 2007
On the revision of the mise en pratique of the definition of the metre and the development of new optical frequency standards 
 23rd CGPM, 2007
Clarification of the definition of the kelvin, unit of thermodynamic temperature 
 23rd CGPM, 2007
On the possible redefinition of certain base units of the International System of Units (SI) 
 CIPM, 2009
Updates to the list of standard frequencies 
 24th CGPM, 2011
On the possible future revision of the International System of Units,
the SI 
 24th CGPM, 2011
On the revision of the mise en pratique of the metre and the development of new optical frequency standards 
 CIPM, 2013
Updates to the list of standard frequencies 
 25th CGPM, 2014
On the future revision of the International System of Units, the SI 
 CIPM, 2015
Updates to the list of standard frequencies 
 CIPM, 2017
On progress towards the possible redefinition of the SI (Decision CIPM/10610) 
 26th CGPM, 2018
On the revision of the International System of Units (SI) 
[Updated 2019]
This appendix lists those decisions of the CGPM and the CIPM that bear directly upon definitions of the units of the SI, prefixes defined for use as part of the SI, and conventions for the writing of unit symbols and numbers. It is not a complete list of CGPM and CIPM decisions. For a complete list, reference must be made to:

Since the SI is not a static convention, but evolves following developments in the science of measurement, some decisions have been abrogated or modified; others have been clarified by additions. In the SI brochure, a number of notes have been added by the BIPM to make the text more understandable; they do not form part of the original text.
The "Chronological list" tab above gives access to the decisions of the CGPM and CIPM in chronological order. In order to make it easy to locate decisions related to particular topics a table of contents is included below, ordered by subject:
Establishment of the SI

9th CGPM, 1948 
decision to establish the SI 

10th CGPM, 1954 
decision on the first six base units 

CIPM, 1956 
decision to adopt the name "Système International d'Unités" 

11th CGPM, 1960 
confirms the name and the abbreviation "SI",
names prefixes from tera to pico,
established the supplementary units rad and sr,
lists some derived units 

CIPM, 1969 
declaration concerning base, supplementary, derived and coherent units, and the use of prefixes 

CIPM, 2001 
"SI units" and "units of the SI" 

23rd CGPM, 2007 
possible redefinition of certain base units of the International System of Units, the SI 

24th CGPM, 2011 
possible future revision of the International System of Units, the SI 

25th CGPM, 2014 
future revision of the International System of Units, the SI 

26th CGPM, 2018 
revision of the International System of Units, the SI 
Base units of the SI
 Decisions of the CGPM and the CIPM relating to the base units of the SI:
SI derived and supplementary units
SI derived units:

12th CGPM, 1964 
accepts the continued use of the curie as a nonSI unit 

13th CGPM, 1967/68 
lists some examples of derived units 

15th CGPM, 1975 
adopts the special names becquerel, Bq, and gray, Gy 

16th CGPM, 1979 
adopts the special name sievert, Sv


CIPM, 1984 
decides to clarify the relationship between absorbed dose (SI unit gray) and dose equivalent (SI unit sievert) 

CIPM, 2002 
modifies the relationship between absorbed dose and dose equivalent 
Supplementary units:
Terminology and the acceptance of units for use with the SI
SI prefixes:
Unit symbols and numbers:
Unit names:

13th CGPM, 1967/68 
abrogates the use of the micron and new candle as units accepted for use with the SI 
The decimal marker:

22nd CGPM, 2003 
decides to allow the use of the point or the comma on the line as the decimal marker 
Units accepted for use with the SI: an example, the litre:

3rd CGPM, 1901 
defines the litre as the volume of 1 kg of water 

11th CGPM, 1960 
requests the CIPM to report on the difference between the litre and the cubic decimetre 

CIPM, 1961 
recommends that volume be expressed in SI units and not in litres 

12th CGPM, 1964 
abrogates the former definition of the litre,
recommends that litre may be used as a special name for the cubic decimetre 

16th CGPM, 1979 
decides, as an exception, to allow both l and L as symbols for the litre 



