Sundarbans National Park is not directly accessible from Kolkata or any other major city in India. You can follow the route direction describe bellow:
Travel by Flight: The nearest airport to reach Sundarbans is the Netaji Subhash International Airport at Dumdum, Kolkata, which is nearly 112 kilometers away from the Sundarbans National Park. It is a very important and busy international airport in eastern India. Domestic and international, both types of aircrafts are available from the airport. Indian Airlines, Air India, some other private and international airlines connect Kolkata with the rest of India and major cities of the Globe. After arriving at Kolkata with flight, you should follow the road or train route to reach the Sundarbans.
Travel by Rail: The nearest railway station is Canning. It is nearly 48 kilometers away from the Sundarbans National Park. From Sealdah (Kolkata) there are many local trains to Canning throughout the day and then may travel with bus to Namkhana, Raidighi, Sonakhali and Najat from where motorboat services are available for Sundarbans.
Travel by Road: From Esplanade (Kolkata) and Howrah, you can get many buses for go to Namkhana(105 kilometer), Sonakhali(100 kilometer) Raidhighi (76 kilometer) Canning (64 km) and Najat (92 km). Taxi are also available from Kolkata, fare may be Rs. 1000/-. All the above-mentioned places are near the Sunderbans National Park and have easy access to waterways.
Travel by Water: If you want to enter into the Tiger Reserve then waterway is the only option. Cruises and Regular Motorboat services are available to reach in the Sundarbans from Namkhana, Raidighi, Sonakhali and Najat. Take a look on approximate time taken between various points:
From Namkhana to -
Sagar Island, 2.5 hours.
Bhagabatpur Crocodile Project, 2.5 hours.
Jambudwip, 3.5 hours.
From Sajnekhali to -
Sudhanyakhali, 40 minutes.
Holiday Island, 3 hours.
Netidhopari, 3.5 hours.
Buridabri (Tiger Project Area), 5 hours.
From Sonakhali to Gosaba, 1 hour
From Raidighi to Kalas, 5 hours
How to reach map - one
You can follow different route to reach in the Sundarbans. But Sonakhali and Canning are the best destinations to access the great Sundarbans, the home of big cat. To reach Canning, you may travel by train or it is also accessible by road. From Sealdah, you can get train to Canning throughout the day. Or can trip by bus from Howrah or from Esplanade (Dharmatala) to Baruipur and then auto-rickshaw to Canning. Some bus services are also available directly to Canning. You can manage taxi or private car too, but it may be very costly. After reach at Canning, you should cross a river with a motorboat and then to reach Sonakhali, you can share three-wheeler pooling van or Auto-rickshaw. Some private bus also available to reach Sonakhali. From Sonakhali, you can get a regular motorboat to entrance into the Sundarbans forests. Or can go to Gosaba or Sajnekhali by motorboat. Both destinations are the entry point to the Sundarbans National Park.
How to reach map - two
From Sealdah, you can go to Sonarpur by train or by bus. From Sonarpur to Dhamakhali via Ghatakpukur by Auto or Bus. From there you can go to Mollakhali by motorboat. And then you should reach at Marijhapi by road. From there yo can entrance into the jungle of Jhongekhali, Sundarbans or to the Buridabri Tiger Project, Sundarbans.
How to reach map - three
Another adventurous way to entrance into Sundarbans, from Canning to Basanti and then Jharkhali by boat. From Jharkhali you can manage motorboat and can go to the river Matla and river Bidyadhari through the cannel Horadanga and Suryamukhee. In this way you may meet with the Dakshin Ray, Royal Bengal Tiger. Kalas island is also accessible in this route.
How to reach map - four
You can also reach at Sundarbans from Jamtala, Raydhighi, Namkhana and Najat. All destination are well connected with Kolkata by government and private buses and then booked motorboat to visit in the Sundarbans National Park.