The calculated distance (air line) between Khān Yūnis and Ḩalḩūl is approximately 50 miles respectively 80 kilometers.
By car or train, the actual journey to Ḩalḩūl is certainly longer, as only the direct route (as the crow flies) between Khān Yūnis and Ḩalḩūl has been calculated here.
Air line (approximately)
80 kilometers
43 nautical miles