Non-SI units mentioned in the SI
This is a list of units that are not defined as part of the International System of Units (SI), but are otherwise mentioned in the SI, because either the General Conference on Weights and Measures (CGPM) accepts their use as being multiples or submultiples of SI-units, they have important contemporary application worldwide, or are otherwise commonly encountered worldwide.
Units officially accepted for use with the SI
|Name||Symbol||Quantity||Value in SI units|
|minute||min||time (SI unit multiple)||1 min = 60 s|
|hour||h||time (SI unit multiple)||1 h = 60 min = 3600 s|
|day||d||time (SI unit multiple)||1 d = 24 h = 1440 min = 86400 s|
|astronomical unit||au||length (SI unit multiple)||1 au = 149597870700 m|
|degree||°||plane angle (dimensionless unit)||1° = (π / 180) rad|
|minute||′||plane angle (dimensionless unit)||1′ = (1 / 60)° = (π / 10800) rad|
|second||″||plane angle (dimensionless unit)||1″ = (1 / 60)′ = (1 / 3600)° = (π / 648000) rad|
|hectare||ha||area (SI unit decimal multiple)||1 ha = 1 hm2 = 10000 m2|
|litre||l or L||volume (SI unit decimal submultiple)||1 L = 1 dm3 = 1000 cm3 = 0.001 m3|
|tonne||t||mass (SI unit decimal multiple)||1 t = 103 kg|
|dalton||Da||mass||1 Da = 1.66053906660(50)×10−27 kg|
|electronvolt||eV||energy||1 eV = 1.602176634×10−19 J|
|neper||Np||level of a field quantity||LF = ln(F / F0) Np|
|level of a power quantity||LP = 1/ ln(P / P0) Np|
|bel, decibel||B||level of a field quantity||LF = 2 log10(F / F0) B|
|level of a power quantity||LP = log10(P / P0) B|
Common units not officially sanctioned
The following table lists units mentioned in side- and footnotes in the 9th SI brochure. Units that occur in historical material recorded in the appendices are not included.
|Name||Symbol||Quantity||Equivalent SI unit|
|gal||Gal||acceleration||1 Gal = 1 cm/s2 = 0.01 m/s2|
|unified atomic mass unit||u||mass||1 u = 1 Da = 1.66053906660(50)×10−27 kg|
|volt-ampere reactive||var||reactive power||1 var = 1 V⋅A|
- International System of Quantities
- International vocabulary of metrology
- Metric prefix
- SI base unit
- SI derived unit
- "SI brochure (9th edition)". BIPM. 2019. §4 Non-SI units that are accepted for use with the SI. Retrieved 2019-05-20.
- "2018 CODATA Value: atomic mass constant". The NIST Reference on Constants, Units, and Uncertainty. NIST. 20 May 2019. Retrieved 2019-05-20.
- The latest CODATA value has been substituted for the value listed in the 9th SI Brochure, since it supersedes that value.
- This is a unit employed in geodesy and geophysics to express acceleration due to gravity.
- As of 2019, the SI brochure no longer lists the unified atomic mass unit (symbol u) as being accepted for use with the SI units, though it notes its equivalence with the dalton in a footnote.