The calculated distance (air line) between Watermael-Boitsfort and Mouscron is approximately 53 miles respectively 85 kilometers.
By car or train, the actual journey to Mouscron is certainly longer, as only the direct route (as the crow flies) between Watermael-Boitsfort and Mouscron has been calculated here.
Air line (approximately)
85 kilometers
46 nautical miles