The calculated distance (air line) between Dún Laoghaire and An Muileann gCearr is approximately 52 miles respectively 84 kilometers.
By car or train, the actual journey to An Muileann gCearr is certainly longer, as only the direct route (as the crow flies) between Dún Laoghaire and An Muileann gCearr has been calculated here.
Air line (approximately)
84 kilometers
45 nautical miles