The calculated distance (air line) between An Muileann gCearr and Ballyfermot is approximately 42 miles respectively 68 kilometers.
By car or train, the actual journey to Ballyfermot is certainly longer, as only the direct route (as the crow flies) between An Muileann gCearr and Ballyfermot has been calculated here.
Air line (approximately)
68 kilometers
37 nautical miles