The calculated distance (air line) between Westport and An Muileann gCearr is approximately 91 miles respectively 147 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 Westport and An Muileann gCearr has been calculated here.
Air line (approximately)
147 kilometers
79 nautical miles