The calculated distance (air line) between Pyŏksŏng-ŭp and Hamhŭng is approximately 167 miles respectively 269 kilometers.
By car or train, the actual journey to Hamhŭng is certainly longer, as only the direct route (as the crow flies) between Pyŏksŏng-ŭp and Hamhŭng has been calculated here.
Air line (approximately)
269 kilometers
145 nautical miles