The calculated distance (air line) between Deba and Donostia / San Sebastián is approximately 19 miles respectively 31 kilometers.
By car or train, the actual journey to Donostia / San Sebastián is certainly longer, as only the direct route (as the crow flies) between Deba and Donostia / San Sebastián has been calculated here.
Air line (approximately)
31 kilometers
17 nautical miles