The calculated distance (air line) between Cartagena and Alhama de Murcia is approximately 30 miles respectively 48 kilometers.
By car or train, the actual journey to Alhama de Murcia is certainly longer, as only the direct route (as the crow flies) between Cartagena and Alhama de Murcia has been calculated here.
Air line (approximately)
48 kilometers
26 nautical miles