The calculated distance (air line) between Saint-Germain-du-Puy and Rouen is approximately 174 miles respectively 280 kilometers.
By car or train, the actual journey to Rouen is certainly longer, as only the direct route (as the crow flies) between Saint-Germain-du-Puy and Rouen has been calculated here.
Air line (approximately)
280 kilometers
151 nautical miles