The calculated distance (air line) between Kilkenny and Dún Laoghaire is approximately 64 miles respectively 103 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Kilkenny and Dún Laoghaire has been calculated here.
Air line (approximately)
103 kilometers
56 nautical miles