The calculated distance (air line) between Nahāvand and Sarpol-e Z̄ahāb is approximately 145 miles respectively 233 kilometers.
By car or train, the actual journey to Sarpol-e Z̄ahāb is certainly longer, as only the direct route (as the crow flies) between Nahāvand and Sarpol-e Z̄ahāb has been calculated here.
Air line (approximately)
233 kilometers
126 nautical miles