The calculated distance (air line) between Donostia / San Sebastián and Boucau is approximately 30 miles respectively 48 kilometers.
By car or train, the actual journey to Boucau is certainly longer, as only the direct route (as the crow flies) between Donostia / San Sebastián and Boucau has been calculated here.
Air line (approximately)
48 kilometers
26 nautical miles