The calculated distance (air line) between Ballyfermot and An Muileann gCearr is approximately 42 miles respectively 68 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 Ballyfermot and An Muileann gCearr has been calculated here.
Air line (approximately)
68 kilometers
37 nautical miles