Laser Helpers

International System of Units

in Reference

The General Conference on Weights and Measures (CGPM) was formed by diplomatic accord and subsequently formulated the Treaty of the Meter. Originally, 17 nations (the United States inclusive) signed the agreement in Paris on May 20, 1875 with 48 nations currently designated as members.

The International System of Units – SI (derived from: Systeme International d’Unites) is administered by the International Bureau of Weights and Measures and periodically convenes its General Conference on Weights and Measures to evaluate measurement requirements.

The SI were formally adopted by CGPM in 1960. They consist of seven base units which, by convention are without reference to any other unit(s), and therefore regarded as independent. There are 22 other derived units which are formed according to various combinations with the base units.

Seven SI Base Units
Base QuantityNameSymbol
lengthmeterm
masskilogramkg
timeseconds
electric currentampereA
thermodynamic
temperature
kelvinK
amount of substancemolemol
luminous intensitycandelacd
Sampling of Laser Photonics Derived Quantities
Derived
Quantity
NameSymbolExpressed in
SI Base Units
plane angleradianradm·m-1 = 1
solid anglesteradiansrm2·m-2 = 1
frequencyhertzHzs-1
energy, work,
quantity of heat
jouleJm2·kg·s-2
power,
radiant flux
wattWm2·kg·s-3
SI Prefixes & Symbols
Denoting Powers of 10
PrefixMultipleSymbol
yotta1024Y
zetta1021Z
exa1018E
peta1015P
tera1012T
giga109G
mega106M
kilo103k
hecto102h
deca10da
deci10-1d
centi10-2c
milli10-3m
micro10-6mu or µ
nano10-9n
pico10-12p
femto10-15f
atto10-18a
zepto10-21z
yocto10-24y