The calculated distance (air line) between Āmol and Gonbad-e Kāvūs is approximately 165 miles respectively 265 kilometers.
By car or train, the actual journey to Gonbad-e Kāvūs is certainly longer, as only the direct route (as the crow flies) between Āmol and Gonbad-e Kāvūs has been calculated here.
Air line (approximately)
265 kilometers
143 nautical miles