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