The calculated distance (air line) between Chapelle-lez-Herlaimont and Ostend is approximately 78 miles respectively 126 kilometers.
By car or train, the actual journey to Ostend is certainly longer, as only the direct route (as the crow flies) between Chapelle-lez-Herlaimont and Ostend has been calculated here.
Air line (approximately)
126 kilometers
68 nautical miles