The calculated distance (air line) between Klagenfurt am Wörthersee and Hietzing is approximately 143 miles respectively 229 kilometers.
By car or train, the actual journey to Hietzing is certainly longer, as only the direct route (as the crow flies) between Klagenfurt am Wörthersee and Hietzing has been calculated here.
Air line (approximately)
229 kilometers
124 nautical miles