The calculated distance (air line) between Donaustadt and Klagenfurt am Wörthersee is approximately 150 miles respectively 241 kilometers.
By car or train, the actual journey to Klagenfurt am Wörthersee is certainly longer, as only the direct route (as the crow flies) between Donaustadt and Klagenfurt am Wörthersee has been calculated here.
Air line (approximately)
241 kilometers
130 nautical miles