The calculated distance (air line) between Rostov-na-Donu and Donskoy is approximately 28 miles respectively 45 kilometers.
By car or train, the actual journey to Donskoy is certainly longer, as only the direct route (as the crow flies) between Rostov-na-Donu and Donskoy has been calculated here.
Air line (approximately)
45 kilometers
24 nautical miles