What is r in pv=nrt?

In the equation pv=nrt, "r" stands for the gas constant. Its value is constant at 8.3145 J/(mol.K) for any ideal gas at standard temperature and pressure (STP), which is defined as 0°C or 273.15 K and 1 atm pressure. The gas constant is used to relate the pressure, volume, and temperature of a gas sample to the number of moles of gas present. It is derived from a combination of the ideal gas law and the Boltzmann constant, which relates the average kinetic energy of gas particles to the temperature of the gas sample.