The calculated distance (air line) between Carrigaline and Dún Laoghaire is approximately 140 miles respectively 225 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Carrigaline and Dún Laoghaire has been calculated here.
Air line (approximately)
225 kilometers
121 nautical miles