The calculated distance (air line) between Bet Shemesh and Kfar Saba is approximately 31 miles respectively 50 kilometers.
By car or train, the actual journey to Kfar Saba is certainly longer, as only the direct route (as the crow flies) between Bet Shemesh and Kfar Saba has been calculated here.
Air line (approximately)
50 kilometers
27 nautical miles