The calculated distance (air line) between Ashton-under-Lyne and Birkenhead is approximately 38 miles respectively 62 kilometers.
By car or train, the actual journey to Birkenhead is certainly longer, as only the direct route (as the crow flies) between Ashton-under-Lyne and Birkenhead has been calculated here.
Air line (approximately)
62 kilometers
33 nautical miles