The calculated distance (air line) between Ramat HaSharon and Rishon LeTsiyyon is approximately 12 miles respectively 20 kilometers.
By car or train, the actual journey to Rishon LeTsiyyon is certainly longer, as only the direct route (as the crow flies) between Ramat HaSharon and Rishon LeTsiyyon has been calculated here.
Air line (approximately)
20 kilometers
11 nautical miles