The calculated distance (air line) between Salzburg and Trostberg an der Alz is approximately 28 miles respectively 44 kilometers.
By car or train, the actual journey to Trostberg an der Alz is certainly longer, as only the direct route (as the crow flies) between Salzburg and Trostberg an der Alz has been calculated here.
Air line (approximately)
44 kilometers
24 nautical miles