The calculated distance (air line) between Chhāgalnāiya and Manikchari is approximately 25 miles respectively 40 kilometers.
By car or train, the actual journey to Manikchari is certainly longer, as only the direct route (as the crow flies) between Chhāgalnāiya and Manikchari has been calculated here.
Air line (approximately)
40 kilometers
21 nautical miles