The calculated distance (air line) between Lausanne and La Chaux-de-Fonds is approximately 41 miles respectively 67 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 Lausanne and La Chaux-de-Fonds has been calculated here.
Air line (approximately)
67 kilometers
36 nautical miles