The calculated distance (air line) between South Dublin and An Muileann gCearr is approximately 44 miles respectively 71 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 South Dublin and An Muileann gCearr has been calculated here.
Air line (approximately)
71 kilometers
38 nautical miles