The calculated distance (air line) between Brest and Saint-Martin-des-Champs is approximately 32 miles respectively 52 kilometers.
By car or train, the actual journey to Saint-Martin-des-Champs is certainly longer, as only the direct route (as the crow flies) between Brest and Saint-Martin-des-Champs has been calculated here.
Air line (approximately)
52 kilometers
28 nautical miles