SI derived units are part of the SI system of measurement units and are derived from the seven SI base units.

Dimensionless derived units

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The following SI units are actually dimensionless ratios, formed by dividing two identical SI units. They are therefore considered by the BIPM to be derived. Formally, their SI unit is simply the number 1, but they are given these special names, for use whenever the lack of a unit might be confusing.

Derived units with special names

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Base units can be put together to derive units of measurement for other quantities. Some have been given names.

Other quantities and units

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Conversion between kelvins and degrees Celsius

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A change in temperature of 1°C is equal to a change in temperature of 1K.

Temperature in °C = Temperature in kelvins –273.15

Thus, one could think of the Kelvin scale as the same as the Celsius scale, with its zero point moved down to absolute zero. This perspective is historically accurate; however, it has become more convenient to fix the standard for the kelvin, and thus the Celsius scale is derived from that standard (i.e., it now depends on absolute zero and the triple point of water with a 0.01 K offset — the boiling point of water no longer has anything to do with the official definition of degrees Celsius).

Temperature differences are often measured in degrees Celsius; however, it doesn't matter: differences in temperature are equivalent whether kelvins or degrees Celsius are used.

Therefore, a change in temperature (ΔT), when expressed in an equation, can be calculated using either kelvins or degrees celsius so long as one is consistent.

See also

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• SI
• SI base unit
• SI prefix
• Planck units

References

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• I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC: Quantities, Units and Symbols in Physical Chemistry, 2nd edition (June 1993), Blackwell Science Inc (p. 72)

SI units | SI derived units

Unitats derivades del SI | Afledte SI-enheder | SI-süsteemi ühikud | Unidad derivada del SI | Unités dérivées du système international | SI 유도 단위 | SI izvedene jedinice | Unitates derivate del SI | SI származtatott egység | Natuurkundige grootheden en eenheden | SI組立単位 | Jednostka pochodna układu SI | Izpeljane enote SI | СИ изведене јединице | SI (härledd enhet) | 国际单位制导出单位