The calculated distance (air line) between Romont and La Chaux-de-Fonds is approximately 28 miles respectively 45 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 Romont and La Chaux-de-Fonds has been calculated here.
Air line (approximately)
45 kilometers
25 nautical miles