Planning Manali from Kolkata is really a two part exercise. First you decide how to cover the long stretch from Kolkata to the mountains. Then you choose the Manali itinerary itself.
There is no direct road or rail line that drops you in Manali. Almost everyone flies or takes a train to a northern hub, and then continues by road into the Kullu Valley.
For most Kolkata travellers, Delhi and Chandigarh are the two most practical gateways. Delhi has the widest flight and train connectivity. Chandigarh sits closer to Manali by road, which shortens the final leg when the timing works.
Bhuntar, the small Kullu Manali airport, is the closest airport to Manali on the map. In practice, flight options and schedules there are limited, so Delhi or Chandigarh often turns out to be the more workable choice. Live schedules for your dates decide this.
Because starting points differ from one package to another, the cleanest way to plan is to tell us your dates, group size, transport preference and hotel level. We can then build a ground itinerary that fits your available days, rather than asking you to force your trip into a fixed template.