The calculated distance (air line) between Trieste and Šempeter pri Gorici is approximately 20 miles respectively 33 kilometers.
By car or train, the actual journey to Šempeter pri Gorici is certainly longer, as only the direct route (as the crow flies) between Trieste and Šempeter pri Gorici has been calculated here.
Air line (approximately)
33 kilometers
18 nautical miles