The calculated distance (air line) between Zheleznodorozhnyy and Kupavna is approximately 4 miles respectively 7 kilometers.
By car or train, the actual journey to Kupavna is certainly longer, as only the direct route (as the crow flies) between Zheleznodorozhnyy and Kupavna has been calculated here.
Air line (approximately)
7 kilometers
4 nautical miles