The calculated distance (air line) between Hwangju-ŭp and Kaesŏng is approximately 64 miles respectively 103 kilometers.
By car or train, the actual journey to Kaesŏng is certainly longer, as only the direct route (as the crow flies) between Hwangju-ŭp and Kaesŏng has been calculated here.
Air line (approximately)
103 kilometers
56 nautical miles