The calculated distance (air line) between Baie-Mahault and Basse-Terre is approximately 21 miles respectively 34 kilometers.
By car or train, the actual journey to Basse-Terre is certainly longer, as only the direct route (as the crow flies) between Baie-Mahault and Basse-Terre has been calculated here.
Air line (approximately)
34 kilometers
18 nautical miles