The calculated distance (air line) between Heppenheim an der Bergstrasse and Dortmund is approximately 139 miles respectively 224 kilometers.
By car or train, the actual journey to Dortmund is certainly longer, as only the direct route (as the crow flies) between Heppenheim an der Bergstrasse and Dortmund has been calculated here.
Air line (approximately)
224 kilometers
121 nautical miles