The calculated distance (air line) between Sankt Leonhard and Klagenfurt am Wörthersee is approximately 63 miles respectively 101 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 Sankt Leonhard and Klagenfurt am Wörthersee has been calculated here.
Air line (approximately)
101 kilometers
54 nautical miles