The calculated distance (air line) between Knocklyon and An Muileann gCearr is approximately 45 miles respectively 72 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 Knocklyon and An Muileann gCearr has been calculated here.
Air line (approximately)
72 kilometers
39 nautical miles