The calculated distance (air line) between Mandalay and Pyin Oo Lwin is approximately 24 miles respectively 39 kilometers.
By car or train, the actual journey to Pyin Oo Lwin is certainly longer, as only the direct route (as the crow flies) between Mandalay and Pyin Oo Lwin has been calculated here.
Air line (approximately)
39 kilometers
21 nautical miles