The calculated distance (air line) between Ar Rām wa Ḑāḩiyat al Barīd and Idhnā is approximately 25 miles respectively 41 kilometers.
By car or train, the actual journey to Idhnā is certainly longer, as only the direct route (as the crow flies) between Ar Rām wa Ḑāḩiyat al Barīd and Idhnā has been calculated here.
Air line (approximately)
41 kilometers
22 nautical miles