The calculated distance (air line) between Sinaia and Piatra Neamţ is approximately 115 miles respectively 184 kilometers.
By car or train, the actual journey to Piatra Neamţ is certainly longer, as only the direct route (as the crow flies) between Sinaia and Piatra Neamţ has been calculated here.
Air line (approximately)
184 kilometers
99 nautical miles