The calculated distance (air line) between Bonn and Höhr-Grenzhausen is approximately 33 miles respectively 52 kilometers.
By car or train, the actual journey to Höhr-Grenzhausen is certainly longer, as only the direct route (as the crow flies) between Bonn and Höhr-Grenzhausen has been calculated here.
Air line (approximately)
52 kilometers
28 nautical miles