Base units Terms Explained
Derived units are formed by powers, products or quotients of the base units and are unlimited in number; Derived units are associated with derived quantities, for example velocity is a quantity that is derived from the base quantities of time and distance which, in SI, has the dimensions metres per second (symbol m/s). The dimensions of derived units can be expressed in terms of the dimensions of the base units.
Some derived units have special names, for example the unit of force is the newton. Coherent units (such as those in SI) are derived units that contain no numerical factor other than 1: in the example above, one newton is the force required to accelerate a mass of one kilogram by one metre per second squared. Since the SI units of mass and acceleration are kg and m⋅s^{−2}respectively and F ∝ m × a, the units of force (and hence of newtons) is formed by multiplication to give kg⋅m⋅s^{−2}. Since the newton is part of a coherent set of units, the constant of proportionality is 1.
Name  Symbol  Quantity  Expressed in terms of other SI units  Expressed in terms of SI base units 

radian  rad  angle  1  m/m 
steradian  sr  solid angle  1  m^{2}/m^{2} 
hertz  Hz  frequency  s^{−1}  
newton  N  force, weight  kg⋅m⋅s^{−2}  
pascal  Pa  pressure, stress  N/m^{2}  kg⋅m^{−1}⋅s^{−2} 
joule  J  energy, work, heat  N⋅m  kg⋅m^{2}⋅s^{−2} 
watt  W  power, radiant flux  J/s  kg⋅m^{2}⋅s^{−3} 
coulomb  C  electric charge or quantity of electricity  s⋅A  
volt  V  voltage (electrical potential difference), electromotive force  W/A  kg⋅m^{2}⋅s^{−3}⋅A^{−1} 
farad  F  electric capacitance  C/V  kg^{−1}⋅m^{−2}⋅s^{4}⋅A^{2} 
ohm  Ω  electric resistance, impedance, reactance  V/A  kg⋅m^{2}⋅s^{−3}⋅A^{−2} 
siemens  S  electrical conductance  A/V  kg^{−1}⋅m^{−2}⋅s^{3}⋅A^{2} 
weber  Wb  magnetic flux  V⋅s  kg⋅m^{2}⋅s^{−2}⋅A^{−1} 
tesla  T  magnetic field strength  Wb/m^{2}  kg⋅s^{−2}⋅A^{−1} 
henry  H  inductance  Wb/A  kg⋅m^{2}⋅s^{−2}⋅A^{−2} 
degree Celsius  °C  temperature relative to 273.15 K  K  
lumen  lm  luminous flux  cd⋅sr  cd 
lux  lx  illuminance  lm/m^{2}  m^{−2}⋅cd 
becquerel  Bq  radioactivity (decays per unit time)  s^{−1}  
gray  Gy  absorbed dose (of ionizing radiation)  J/kg  m^{2}⋅s^{−2} 
sievert  Sv  equivalent dose (of ionizing radiation)  J/kg  m^{2}⋅s^{−2} 
katal  kat  catalytic activity  s^{−1}⋅mol  
Notes 1. The radian and steradian, once given special status, are now considered dimensionless derived units.2. The ordering of this table is such that any derived unit is based only on base units or derived units that precede it in the table. 
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