The calculated distance (air line) between Castel San Pietro Terme and Sasso Marconi is approximately 16 miles respectively 27 kilometers.
By car or train, the actual journey to Sasso Marconi is certainly longer, as only the direct route (as the crow flies) between Castel San Pietro Terme and Sasso Marconi has been calculated here.
Air line (approximately)
27 kilometers
14 nautical miles