The calculated distance (air line) between Brunn am Gebirge and Sankt Pölten is approximately 31 miles respectively 49 kilometers.
By car or train, the actual journey to Sankt Pölten is certainly longer, as only the direct route (as the crow flies) between Brunn am Gebirge and Sankt Pölten has been calculated here.
Air line (approximately)
49 kilometers
27 nautical miles