The calculated distance (air line) between Duisburg and Mons-en-Barœul is approximately 168 miles respectively 270 kilometers.
By car or train, the actual journey to Mons-en-Barœul is certainly longer, as only the direct route (as the crow flies) between Duisburg and Mons-en-Barœul has been calculated here.
Air line (approximately)
270 kilometers
146 nautical miles