There are various transportation ways for the answer to the question as to how to reach Nathula pass.
By Air: If you are choosing to fly, the nearest airport is Bagdogra Airport. It is connected to cities like Delhi, Bangalore, and Kolkata. Almost all major airlines have flights to this airport. You can avail taxi or bus from there to reach Gangtok.
By Rail: The nearest railway station is Jalpaiguri, 98 km from Gangtok. You can take a taxi from here to Gangtok.
By Road: If you are choosing road, Sikkim is well connected through good roads. Regular bus services are available from Bagdogra, Darjeeling, Kolkata and Kalimpong.
Reach Nathula Pass
The only way to reach Gangtok to Nathula pass is through a drive from Gangtok. Nathula is 54 km east of Gangtok, the capital of Sikkim. Because of bad road condition only sturdy vehicles such as Innova, Bolero, and Scorpio should be taken to Nathula. Vehicles are available for rent in Gangtok or you can also share a cab till Nathula Pass with other tourists. The road from Gangtok to Nathula Pass is steep and slippery but decently maintained, except in a few places. Sometimes due to snow landslides and other road conditions, traffic gets held up for hours in this route.
Tourists are allowed to take a round trip package from an authorized tour operator in Gangtok. Vehicles from Sikkim government approved tour operators are only permitted for Nathula. From Gangtok shared jeeps and reserved vehicles like Scorpio, Innova, Bolero, Sumo, etc. are also available for group tours that operate on per person rates. The cost can vary depending on season. During peak tourist season (April to June, and October to November), the shared vehicle would cost you about INR 700 per person for Tsomgo Lake, Baba Mandir and Nathula including permit fee. Reserved vehicles like Scorpio or Innova would cost newcomers around INR 7,000 including all permits. Other than the peak season, shared vehicles are usually not available while reserved vehicles cost lower.
Only Indian nationals with a valid permit can visit Nathula Pass. A permit can be obtained by applying to the Tourism and Civil Aviation Department or through a registered travel agency. The requirements for the same are a photo ID proof and two passport size photographs. The Nathula Pass permit cost is INR 200 per person.