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