<p>A three-dimensional numerical simulation has been carried out for the evaporation of an isolated <i>n</i>-heptane (<i>n</i>-C₇H₁₆) droplet by varying the ambient gas. The main focus is on the effects of inert gas as ambient gas on evaporation. The inert gas effects on evaporation were analysed by tracking the droplet diameter by using the d² law. A comparative analysis was conducted using air, argon, helium and nitrogen as ambient gases under low-pressure and low-temperature in microgravity conditions. In addition, the study has been carried out particularly with argon and helium as ambient gas at high temperature and pressure in the range of 1000 K to 1200 K and 0.1 MPa to 2 MPa. The computational results of normalized squared droplet diameter (<i>d/d</i>₀)² with respect to time (<i>t/d</i><Stack> ₀ ² </Stack>) were compared with experimental data for validation. There is strong agreement between the experimental and numerical results. The result shows that droplet lifetime decreases with increasing the temperature and increases with increasing the pressure. The lifetime of the <i>n</i>-heptane droplet extends with argon as the ambient gas, while helium significantly decreases droplet life time compared to air and nitrogen across various temperatures. Thus, the choice of ambient gas profoundly impacts droplet evaporation dynamics.</p>