|Values of R|| Units |
|8.20574587 × 10-5||m3·atm·K-1·mol-1|
|8.314472 × 107||erg·K-1·mol-1|
|1716 (Air only)||ft·lb·°R-1·slug-1|
|286.9 (Air only)||N·m·kg-1·K-1|
|286.9 (Air only)||J·kg-1·K-1|
Its value is:
The gas constant has the same units as specific entropy.
The specific gas constant of a gas or a mixture of gases () is given by the universal gas constant, divided by the molar mass () of the gas/mixture.
It is common to represent the specific gas constant by the symbol . In such cases the context and/or units of should make it clear as to which gas constant is being referred to. For example, the equation for the speed of sound is usually written in terms of the specific gas constant.
The specific gas constant of dry air is
The USSA1976 does recognize, however, that this value is not consistent with the cited values for the Avogadro constant and the Boltzmann constant. This disparity is not a significant departure from accuracy, and USSA1976 uses this value of R for all the calculations of the standard atmosphere. When using the ISO value of R, the calculated pressure increases by only 0.62 pascals at 11,000 meters (the equivalent of a difference of only 0.174 meters – or 6.8 inches) and an increase of 0.292 pascals at 20,000 meters (the equivalent of a difference of only 0.338 meters – or 13.2 inches).