List of metric units


Metric units are units based on the metre, gram or second and decimal multiples or sub-multiples of these. According to Schadow and McDonald, metric units, in general, are those units "defined 'in the spirit' of the metric system, that emerged in late 18th century France and was rapidly adopted by scientists and engineers. Metric units are in general based on reproducible natural phenomena and are usually not part of a system of comparable units with different magnitudes, especially not if the ratios of these units are not powers of 10. Instead, metric units use multiplier prefixes that magnifies or diminishes the value of the unit by powers of ten."
The most widely used examples are the units of the International System of Units. By extension they include units of electromagnetism from the CGS and SI units systems, and other units for which use of SI prefixes has become the norm. Other unit systems using metric units include:

SI units

The first group of metric units are those that are at present defined as units within the International System of Units. In its most restrictive interpretation, this is what may be meant when the term metric unit is used.
The unit one is the unit of a quantity of dimension one. It is the neutral element of any system of units.
Furthermore, there are twenty-four metric prefixes that can be combined with any of these units except one and kilogram to form further units of the SI. For mass, the same prefixes are applied to the gram instead of the kilogram.

Non-SI metric units

There are several metric systems, most of which have become disused or are still used in only niche disciplines. Systems are listed with named units that are associated with them.

CGS

The centimetre–gram–second system of units is based on three base units: centimetre, gram and second. Its subsystems have different defining equations for their systems of quantities for defining electromagnetic quantities and hence the associated units, with CGS-Gaussian units being selected from each of the other two subsystems.
The CGS-to-SI correspondence of electromagnetic units as given was exact prior to the 2019 revision of the SI, until which the magnetic constant μ0 was defined as. As from the redefinition, μ0 has an inexactly known value when expressed in SI units, with the exactness of the electromagnetic unit correspondence given here being affected accordingly.

CGS nonelectromagnetic units

CGS-ESU electromagnetic units

CGS-EMU electromagnetic units

CGS-Gaussian electromagnetic units

MTS

MKS

MKpS units

Other metric units

Length

Area

Volume

Reciprocal length

Time

Reciprocal time

Reciprocal time squared

Speed

Acceleration

Flow rate

Mass

Linear mass density

Pressure

Energy

Viscosity

Electrical

Electromagnetic radiation

Radioactivity

Concentration

Acoustics