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The IIT Delhi campus is located in Hauz Khas in South Delhi, with the Main Gate around 1.2 km from the nearest Metro Station of Hauz Khas. Roughly, it is 12-13 kms away from the New Delhi Railway Station opening into Ajmeri Gate, and about the same from the Hazrat Nizamuddin station or the IGI airport.
The Campus is well connected by road to each of these three major arrival points. As such, you can readily hire a taxi, cabs or an auto-rickshaw from any of these to reach the Campus, but the metro will be by far the most economical means.
Do read this primer on getting to IIT Delhi.