The calculated distance (air line) between Trieste and Ronchi dei Legionari is approximately 18 miles respectively 29 kilometers.
By car or train, the actual journey to Ronchi dei Legionari is certainly longer, as only the direct route (as the crow flies) between Trieste and Ronchi dei Legionari has been calculated here.
Air line (approximately)
29 kilometers
16 nautical miles