The calculated distance (air line) between Aix-en-Provence and Marseille 12 is approximately 16 miles respectively 26 kilometers.
By car or train, the actual journey to Marseille 12 is certainly longer, as only the direct route (as the crow flies) between Aix-en-Provence and Marseille 12 has been calculated here.
Air line (approximately)
26 kilometers
14 nautical miles