The calculated distance (air line) between Uttar Char Fasson and Sandwīp is approximately 51 miles respectively 83 kilometers.
By car or train, the actual journey to Sandwīp is certainly longer, as only the direct route (as the crow flies) between Uttar Char Fasson and Sandwīp has been calculated here.
Air line (approximately)
83 kilometers
45 nautical miles