The Classical Nucleation Theory (CNT) has been a dominant model in understanding the self-assembly of new thermodynamic phases. CNT provides significant explanations to processes such as aerosol formation and cloud condensation. In this work, we generated the nucleation free energy profiles of normal alkanes (n-propane, n-octane and n-dodecane) at five different temperatures using the grand-canonical version of the nucleation algorithm. From these free energy profiles, characteristic $ \Omega $ ($ \equiv $$ \sigma /\rho ^{2/3} $) values were obtained. Using the density, $ \rho $ values from United-Atom Transferable Potentials for Phase Equilibria (TraPPE-UA) force field and the obtained $ \Omega $ values, we calculated the corresponding surface tension, $ \sigma $ values of these n-alkane systems at different temperatures. Values obtained are within reasonable agreement with experimental data.