The calculated distance (air line) between Saint-Quentin-en-Yvelines and Boulogne-Billancourt is approximately 11 miles respectively 18 kilometers.
By car or train, the actual journey to Boulogne-Billancourt is certainly longer, as only the direct route (as the crow flies) between Saint-Quentin-en-Yvelines and Boulogne-Billancourt has been calculated here.
Air line (approximately)
18 kilometers
10 nautical miles