The calculated distance (air line) between Carlow and Dún Laoghaire is approximately 45 miles respectively 73 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Carlow and Dún Laoghaire has been calculated here.
Air line (approximately)
73 kilometers
39 nautical miles