The International System of Units ( SI )

  1. In all there are seven SI base units:
    1. the meter for distance,
    2. the kilogram for mass,
    3. the second for time,
    4. the ampere for electric current,
    5. the kelvin for temperature,
    6. the mole for amount of substance, and
    7. the candela for intensity of light.

Other SI units, SI derived units, are defined merely algebraically in terms of the fundamental units.

  1. the radian and steradian for plane and solid angles, respectively;
  2. the newton for force and the pascal for pressure;
  3. the joule for energy and the watt for power;
  4. the degree Celsius for everyday measurement of temperature;
  5. units for measurement of electricity:
    1. the coulomb (charge)
    2. the volt (potential)
    3. the farad (capacitance)
    4. ohm (resistance),
    5. siemens (conductance)
  6. units for measurement of magnetism:
    1. the weber (flux)the
    2. tesla (flux density),
    3. henry (inductance);
  1. For flux of light
    1. the lumen
    2. the lux for illuminance;
    3. the becquerel for radioactivity;
    4. the gray
    5. the sievert for radiation dose
    6. the katal, a unit of catalytic activity used in biochemistry.
  • 29 base and derived units, and additional units, including:
    1. the traditional mathematical units for measuring angles
      1.  The degree indicated by (° or deg)
      2.  The arcminute
      3.  The arcsecond)
    2. the traditional units of civil time (minute
      1. The The hour
      2. The day
      3. The year)
    3. two metric units commonly used in ordinary life:
      1. the liter
      2. the tonne (metric ton) for large masses
    4. the logarithmic units
      1. The bel
      2. The neper
      (and their multiples, such as the decibel)
    5. three non-metric scientific units whose values represent important physical constants:
      1. the astronomical unit
      2. the atomic mass unit or dalton
      3. the electronvolt
  • Defined in relation to a SI unit.
    1. the nautical mile and knot, units traditionally used at sea and in meteorology;
    2. the are and hectare, common metric units of area;
    3. the bar, a pressure unit, and its commonly-used multiples such as the millibar in meteorology and the kilobar in engineering;
    4. the angstrom and the barn, units used in physics and astronomy.

    For multiples of approved units, a list of prefixes.