The calculated distance (air line) between Rostov-na-Donu and Semikarakorsk is approximately 54 miles respectively 87 kilometers.
By car or train, the actual journey to Semikarakorsk is certainly longer, as only the direct route (as the crow flies) between Rostov-na-Donu and Semikarakorsk has been calculated here.
Air line (approximately)
87 kilometers
47 nautical miles