Thermalization is a vital feature that enables the study of hydrodynamic evolution of the medium produced in nuclear collisions at relativistic energies. Here, we obtain the variation of Knudsen number ($Kn$) to study the degree of thermalization in an excluded volume hadron resonance gas model. $Kn$ along with other parameters like Reynolds number ($Re$) and Mach number ($Ma$) give insights into the nature of the flow in a system. The dependence of these dimensionless parameters on system size and baryonic chemical potential ($\mu_B$) are studied. The obtained values of the parameters ($Kn << 1$, $Ma \sim 1$ and $Re >> 1$) indicate the occurrence of compressible inviscid flows at high temperatures close to the QCD phase transition region ($T \sim150 -170$ MeV). The degree of thermalization of hadron gas estimated is comparable over different system sizes, indicating the applicability of hydrodynamics in interpreting the results from high multiplicity pp to heavy-ion collisions.