The calculated distance (air line) between Youghal and Dún Laoghaire is approximately 117 miles respectively 189 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Youghal and Dún Laoghaire has been calculated here.
Air line (approximately)
189 kilometers
102 nautical miles