The calculated distance (air line) between Kostanjevica na Krki and Novo Mesto is approximately 13 miles respectively 20 kilometers.
By car or train, the actual journey to Novo Mesto is certainly longer, as only the direct route (as the crow flies) between Kostanjevica na Krki and Novo Mesto has been calculated here.
Air line (approximately)
20 kilometers
11 nautical miles