The calculated distance (air line) between Rosignano Solvay-Castiglioncello and Florence is approximately 49 miles respectively 78 kilometers.
By car or train, the actual journey to Florence is certainly longer, as only the direct route (as the crow flies) between Rosignano Solvay-Castiglioncello and Florence has been calculated here.
Air line (approximately)
78 kilometers
42 nautical miles