The calculated distance (air line) between Gaza and Dayr al Balaḩ is approximately 9 miles respectively 14 kilometers.
By car or train, the actual journey to Dayr al Balaḩ is certainly longer, as only the direct route (as the crow flies) between Gaza and Dayr al Balaḩ has been calculated here.
Air line (approximately)
14 kilometers
8 nautical miles