Value of $\mathrm{R}$ in $\mathrm{SI}$ units is

The ideal gas equation is $\mathrm{PV}=\mathrm{nRT}$ and $\mathrm{R}$  is a universal gas constant.

Here:

P represents pressure,
V is the volume,
n denotes the number of moles of the gas,
R is the universal gas constant, and
T stands for temperature (in Kelvin).

The universal gas constant, R, is a fundamental physical constant that links the physical properties of gases. Its value depends on the units chosen for pressure, temperature, and volume. For example, when pressure is measured in pascals (Pa), volume in cubic meters (m³), and temperature in kelvins (K), the value of R is approximately 8.315 J mol⁻¹ K⁻¹ (joules per mole per kelvin).

Hence, $\mathrm{R}=$8.315 $\mathrm{J}{ \mathrm{K}}^{-1}$ mole^-1