The calculated distance (air line) between Saint-Hilaire-de-Riez and Brest is approximately 165 miles respectively 266 kilometers.
By car or train, the actual journey to Brest is certainly longer, as only the direct route (as the crow flies) between Saint-Hilaire-de-Riez and Brest has been calculated here.
Air line (approximately)
266 kilometers
144 nautical miles