The calculated distance (air line) between Cagnes-sur-Mer and Saint-Étienne is approximately 183 miles respectively 294 kilometers.
By car or train, the actual journey to Saint-Étienne is certainly longer, as only the direct route (as the crow flies) between Cagnes-sur-Mer and Saint-Étienne has been calculated here.
Air line (approximately)
294 kilometers
159 nautical miles