The calculated distance (air line) between Kaesŏng and P’yŏngsŏng is approximately 96 miles respectively 154 kilometers.
By car or train, the actual journey to P’yŏngsŏng is certainly longer, as only the direct route (as the crow flies) between Kaesŏng and P’yŏngsŏng has been calculated here.
Air line (approximately)
154 kilometers
83 nautical miles