Universal gas constant, is represented by R (not k) is a physical constant and is the constant of proportionality which relate the energy scale to the temperature scale when a mole of particles at the stated temperature is being considered.
k or kB denotes Boltzmann constant and it is microscopic form of gas constant
thus R = N.kB (where N= avogadro's no.)
i.e. kB = R/N
= 8.314/6.022 x 1023 = 1.38 x 10-23 J/K
or 1.38 x 10-16 ergs/ K
R can have the values 0.0821 litre.atm / mol.K , 8.314 J / mol K , 8.2057 m3 .atm / mol.K depending on the conditions.