The calculated distance (air line) between An Muileann gCearr and Blessington is approximately 41 miles respectively 66 kilometers.
By car or train, the actual journey to Blessington is certainly longer, as only the direct route (as the crow flies) between An Muileann gCearr and Blessington has been calculated here.
Air line (approximately)
66 kilometers
36 nautical miles