The calculated distance (air line) between Siegburg and Bochum-Hordel is approximately 48 miles respectively 78 kilometers.
By car or train, the actual journey to Bochum-Hordel is certainly longer, as only the direct route (as the crow flies) between Siegburg and Bochum-Hordel has been calculated here.
Air line (approximately)
78 kilometers
42 nautical miles