The calculated distance (air line) between Salerno and San Marzano sul Sarno is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to San Marzano sul Sarno is certainly longer, as only the direct route (as the crow flies) between Salerno and San Marzano sul Sarno has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles