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