The calculated distance (air line) between Klagenfurt am Wörthersee and Gries is approximately 61 miles respectively 98 kilometers.
By car or train, the actual journey to Gries is certainly longer, as only the direct route (as the crow flies) between Klagenfurt am Wörthersee and Gries has been calculated here.
Air line (approximately)
98 kilometers
53 nautical miles