The calculated distance (air line) between Duisburg and Katwijk aan den Rijn is approximately 113 miles respectively 182 kilometers.
By car or train, the actual journey to Katwijk aan den Rijn is certainly longer, as only the direct route (as the crow flies) between Duisburg and Katwijk aan den Rijn has been calculated here.
Air line (approximately)
182 kilometers
98 nautical miles