The calculated distance (air line) between Nenagh and Dún Laoghaire is approximately 91 miles respectively 146 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Nenagh and Dún Laoghaire has been calculated here.
Air line (approximately)
146 kilometers
79 nautical miles