The calculated distance (air line) between Heppenheim an der Bergstrasse and Duisburg is approximately 148 miles respectively 239 kilometers.
By car or train, the actual journey to Duisburg is certainly longer, as only the direct route (as the crow flies) between Heppenheim an der Bergstrasse and Duisburg has been calculated here.
Air line (approximately)
239 kilometers
129 nautical miles