The calculated distance (air line) between Kostiantynivka and Khartsyzk is approximately 39 miles respectively 63 kilometers.
By car or train, the actual journey to Khartsyzk is certainly longer, as only the direct route (as the crow flies) between Kostiantynivka and Khartsyzk has been calculated here.
Air line (approximately)
63 kilometers
34 nautical miles