The calculated distance (air line) between Sarzana and Castelnovo ne'Monti is approximately 31 miles respectively 50 kilometers.
By car or train, the actual journey to Castelnovo ne'Monti is certainly longer, as only the direct route (as the crow flies) between Sarzana and Castelnovo ne'Monti has been calculated here.
Air line (approximately)
50 kilometers
27 nautical miles