The calculated distance (air line) between Kostanjevica na Krki and Kočevje is approximately 30 miles respectively 49 kilometers.
By car or train, the actual journey to Kočevje is certainly longer, as only the direct route (as the crow flies) between Kostanjevica na Krki and Kočevje has been calculated here.
Air line (approximately)
49 kilometers
26 nautical miles