SI Units
SI Base units
SI (International System of Units) is an Internal Unit System based on 7 Units which are considered independent of Each Other.
Base quantity | Name | Symbol |
---|---|---|
length | meter | m |
mass | kilogram | kg |
time | second | s |
electric current | ampere | A |
thermodynamic temperature | kelvin | K |
amount of substance | mole | mol |
luminous intensity | candela | cd |
SI General Derived Units
SI derived units are calculated based on applying an equation on the SI Derived Units.
Quantity | Name | Symbol |
---|---|---|
area | square meter | m2 |
volume | cubic meter | m3 |
speed, velocity | meter per second | m/s |
acceleration | meter per second squared | m/s2 |
wave number | reciprocal meter | m-1 |
mass density | kilogram per cubic meter | kg/m3 |
specific volume | cubic meter per kilogram | m3/kg |
current density | ampere per square meter | A/m2 |
magnetic field strength | ampere per meter | A/m |
amount-of-substance concentration | mole per cubic meter | mol/m3 |
luminance | candela per square meter | cd/m2 |
mass fraction | kilogram per kilogram, which may be represented by the number 1 | kg/kg = 1 |
SI Derived Units with Special Names and Symbols
There are 22 SI Derived Units with Special Names and Symbols. These 22 Derived Units are combined to create a set of secondary derived SI Units, which will be shown in the table ‘Secondary Derived Units with Special Names and Symbols” down below.
Quantity | Name | Symbol | Expression using other Units | Expression using SI base units |
---|---|---|---|---|
plane angle | radian (a) | rad | – | m·m-1 = 1 (b) |
solid angle | steradian (a) | sr (c) | – | m2·m-2 = 1 (b) |
frequency | hertz | Hz | – | s-1 |
force | newton | N | – | m·kg·s-2 |
pressure, stress | pascal | Pa | N/m2 | m-1·kg·s-2 |
energy, work, quantity of heat | joule | J | N·m | m2·kg·s-2 |
power, radiant flux | watt | W | J/s | m2·kg·s-3 |
electric charge, quantity of electricity | coulomb | C | – | s·A |
electric potential difference, electromotive force |
volt | V | W/A | m2·kg·s-3·A-1 |
capacitance | farad | F | C/V | m-2·kg-1·s4·A2 |
electric resistance | ohm | ![]() |
V/A | m2·kg·s-3·A-2 |
electric conductance | siemens | S | A/V | m-2·kg-1·s3·A2 |
magnetic flux | weber | Wb | V·s | m2·kg·s-2·A-1 |
magnetic flux density | tesla | T | Wb/m2 | kg·s-2·A-1 |
inductance | henry | H | Wb/A | m2·kg·s-2·A-2 |
Celsius temperature | degree Celsius | °C | – | K |
luminous flux | lumen | lm | cd·sr (c) | m2·m-2·cd = cd |
illuminance | lux | lx | lm/m2 | m2·m-4·cd = m-2·cd |
activity (of a radionuclide) | becquerel | Bq | – | s-1 |
absorbed dose, specific energy (imparted), kerma | gray | Gy | J/kg | m2·s-2 |
dose equivalent (d) | sievert | Sv | J/kg | m2·s-2 |
catalytic activity | katal | kat | s-1·mol |
SI Secondary Derived Units with Special Names and Symbols
SI Units mentioned in the following table are derived from other SI Derived Units with Special Names and Symbols, hence we can treat them as SI Secondary Derived Units.
Quantity | Unit | Symbol |
---|---|---|
dynamic viscosity | pascal second | Pa·s |
moment of force | newton meter | N·m |
surface tension | newton per meter | N/m |
angular velocity | radian per second | rad/s |
angular acceleration | radian per second squared | rad/s2 |
heat flux density, irradiance | watt per square meter | W/m2 |
heat capacity, entropy | joule per kelvin | J/K |
specific heat capacity, specific entropy | joule per kilogram kelvin | J/(kg·K) |
specific energy | joule per kilogram | J/kg |
thermal conductivity | watt per meter kelvin | W/(m·K) |
energy density | joule per cubic meter | J/m3 |
electric field strength | volt per meter | V/m |
electric charge density | coulomb per cubic meter | C/m3 |
electric flux density | coulomb per square meter | C/m2 |
permittivity | farad per meter | F/m |
permeability | henry per meter | H/m |
molar energy | joule per mole | J/mol |
molar entropy, molar heat capacity | joule per mole kelvin | J/(mol·K) |
exposure (x and ![]() |
coulomb per kilogram | C/kg |
absorbed dose rate | gray per second | Gy/s |
radiant intensity | watt per steradian | W/sr |
radiance | watt per square meter steradian | W/(m2·sr) |
catalytic (activity) concentration | katal per cubic meter | kat/m3 |