Indian Railways follows a five-digit train numbering scheme where the first digit denotes the train category.

• 0xxxx: Holiday specials and other special trains.
• 1xxxx/2xxxx: Mail/Express trains (superfast if 22xxx).
• 3xx x Kolkata Metro
• 4xxx Other Suburban Delhi Chennai 
• 5xxx: Ordinary Passenger trains.
• 6xxx: MEMU (Mainline Electric Multiple Unit) trains.
• 7xxx: DEMU (Diesel Electric Multiple Unit) trains.
• 8xxx: Suvidha Express trains.
• 9xxx: Mumbai suburban EMU/Vande Metro.

Second digit indicates the zone; rest specify route/division