The calculated distance (air line) between Dunboyne and Dún Laoghaire is approximately 16 miles respectively 26 kilometers.
By car or train, the actual journey to Dún Laoghaire is certainly longer, as only the direct route (as the crow flies) between Dunboyne and Dún Laoghaire has been calculated here.
Air line (approximately)
26 kilometers
14 nautical miles