The calculated distance (air line) between Six-Fours-les-Plages and Marseille is approximately 26 miles respectively 43 kilometers.
By car or train, the actual journey to Marseille is certainly longer, as only the direct route (as the crow flies) between Six-Fours-les-Plages and Marseille has been calculated here.
Air line (approximately)
43 kilometers
23 nautical miles