The calculated distance (air line) between Mariupol and Novoazovs'k is approximately 26 miles respectively 41 kilometers.
By car or train, the actual journey to Novoazovs'k is certainly longer, as only the direct route (as the crow flies) between Mariupol and Novoazovs'k has been calculated here.
Air line (approximately)
41 kilometers
22 nautical miles