The behaviour of an Ideal gas is described by the following equation,

PV = nRT

where,

P = Pressure (bar, atmosphere, Pa)

V = Gaseous volume (m^{3}, cm^{3})

n = number of gaseous moles (dimensionless)

R = Universal gas constant (J/mol.K, lit.atm/mol.K)

T = Temperature of the gas (K, ^{0}C)

The universal gas constant is also known by alternative names such as Ideal gas constant, molar gas constant or simply, gas constant.

The universal gas constant is common for all the gases and the numerical value of this constant depends on the units used to describe the remaining entities in the Ideal gas equation, such as pressure, temperature, and volume.

For different combinations of units, numerical values of Universal gas constant are given by following list,

Units ( P.V / n.T ) Value of R

J/K.mol 8.314

cal/K.mol 1.986

erg/K.mol 8.314X10^{7}

lit.kPa/K.mol 8.314

m^{3}.Pa/K.mol 8.314

cm^{3}.MPa/K.mol 8.314

m^{3}.bar/K.mol 8.314X10^{-5}

cm^{3}.atm/K.mol 82.06

lit.bar/K.mol 8.314X10^{-2}

lit.atm/K.mol 0.082

lit.mmHg/K.mol 62.364

lit.torr/K.mol 62.364

ft.lbf/K.gmol 6.132

ft.lbf/^{0}R.lb-mol 1545.35

ft^{3}.psi/^{0}R.lb-mol 10.732

ft^{3}.atm/^{0}R.lb-mol 0.730

ft^{3}.mmHg/K.lb-mol 998.97