The calculated distance (air line) between Biel/Bienne and La Chaux-de-Fonds is approximately 20 miles respectively 32 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 Biel/Bienne and La Chaux-de-Fonds has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles