Resolution 12 of the 11th CGPM
Système International d'Unités
The 11th Conférence Générale des Poids et Mesures (CGPM),
- Resolution 6 of the 10th CGPM, by which it adopted six base units on which to establish a practical system of measurement for international use:
length metre m mass kilogram kg time second s electric current ampere A thermodynamic temperature degree Kelvin °K luminous intensity candela cd
- Resolution 3 adopted by the Comité International des Poids et Mesures (CIPM) in 1956,
- the recommendation adopted by the CIPM in 1958 concerning an abbreviation for the name of the system, and prefixes to form multiples and submultiples of the units,
- the system founded on the six base units above is called the "Système International d'Unités";
- the international abbreviation of the name of the system is SI;
- names of multiples and submultiples of the units are formed by means of the following prefixes:
Prefix Symbol Multiplying
Prefix Symbol 1 000 000 000 000 = 1012 tera T 0.1 = 10–1 deci d 1 000 000 000 = 109 giga G 0.01 = 10–2 centi c 1 000 000 = 106 mega M 0.001 = 10–3 milli m 1 000 = 103 kilo k 0.000 001 = 10–6 micro µ 100 = 102 hecto h 0.000 000 001 = 10–9 nano n 10 = 101 deca da 0.000 000 000 001 = 10–12 pico p
- the units listed below are used in the system, without excluding others which might be added later.
|mass density (density) kilogram per cubic metre||kilogram per cubic metre||kg/m3|
|speed, velocity||metre per second||m/s|
|angular velocity radian per second||radian per second||rad/s|
|acceleration||metre per second squared||m/s2|
|angular acceleration||radian per second squared||rad/s2|
|force||newton||N||kg · m/s2|
|pressure (mechanical stress)||newton per square metre||N/m2|
|kinematic viscosity||square metre per second||m2/s|
|dynamic viscosity||newton-second per square metre||N · s/m2|
|work, energy, quantity of heat||joule||J||N · m|
|quantity of electricity||coulomb||C||A · s|
|electric field strength volt per metre||volt per metre||V/m|
|capacitance||farad||F||A · s/V|
|magnetic flux||weber||Wb||V · s|
|inductance||henry||H||V · s/A|
|magnetic flux density||tesla||T||Wb/m2|
|magnetic field strength||ampere per metre||A/m|
|luminous flux||lumen||lm||cd · sr|
|luminance||candela per square metre||cd/m2|
The CGPM later abrogated certain of its decisions and extended the list of prefixes:
- The name and symbol for the unit of thermodynamic temperature were modified by the 13th CGPM in 1967 (Resolution 3).
- A seventh base unit, the mole, was adopted by the 14th CGPM in 1971 (Resolution 3).
- Further prefixes were adopted by the 12th CGPM in 1964 (Resolution 8), the 15th CGPM in 1975 (Resolution 10), and the 19th CGPM in 1991 (Resolution 4).
- The 20th CGPM in 1995 abrogated the class of supplementary units in the SI (Resolution 8). These are now considered as derived units.
- The 13th CGPM in 1967 (Resolution 6) specified other units which should be added to this list of derived units. In principle, the list is without limit.
- Modern practice is to use the phrase "amount of heat" rather than "quantity of heat", because the word quantity has a different meaning in metrology.
- Modern practice is to use the phrase "amount of electricity" rather than "quantity of electrcity" (see above).