The calculated distance (air line) between Dalkey and An Muileann gCearr is approximately 54 miles respectively 87 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 Dalkey and An Muileann gCearr has been calculated here.
Air line (approximately)
87 kilometers
47 nautical miles