The calculated distance (air line) between Pyongyang and Pyŏksŏng-ŭp is approximately 69 miles respectively 111 kilometers.
By car or train, the actual journey to Pyŏksŏng-ŭp is certainly longer, as only the direct route (as the crow flies) between Pyongyang and Pyŏksŏng-ŭp has been calculated here.
Air line (approximately)
111 kilometers
60 nautical miles