The calculated distance (air line) between Bochum and Watermael-Boitsfort is approximately 130 miles respectively 210 kilometers.
By car or train, the actual journey to Watermael-Boitsfort is certainly longer, as only the direct route (as the crow flies) between Bochum and Watermael-Boitsfort has been calculated here.
Air line (approximately)
210 kilometers
113 nautical miles