The calculated distance (air line) between Midleton and Dún Laoghaire is approximately 128 miles respectively 206 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Midleton and Dún Laoghaire has been calculated here.
Air line (approximately)
206 kilometers
111 nautical miles