The gas constant, also known as the universal molar gas constant, is a physical constant that appears in an equation defining the behavior of a gas under theoretically ideal conditions. The gas constant is, by convention, symbolized R.
The pressure, volume, amount of substance, and temperature of a gas are related according to the following equation, known as the universal gas equation:
PV = NRT
In terms of the pressure, volume, amount of substance, and temperature, the gas constant is equal to:
R = (PV) / (NT)
The gas constant has been found, by experiment, to have a value of approximately 8.3145 joules per kelvin per mole (J · K-1 · mol-1).
Also see Table of Physical Constants.