The calculated distance (air line) between Altstätten and Biel/Bienne is approximately 109 miles respectively 176 kilometers.
By car or train, the actual journey to Biel/Bienne is certainly longer, as only the direct route (as the crow flies) between Altstätten and Biel/Bienne has been calculated here.
Air line (approximately)
176 kilometers
95 nautical miles