The calculated distance (air line) between Courtry and Saint-Quentin-en-Yvelines is approximately 29 miles respectively 46 kilometers.
By car or train, the actual journey to Saint-Quentin-en-Yvelines is certainly longer, as only the direct route (as the crow flies) between Courtry and Saint-Quentin-en-Yvelines has been calculated here.
Air line (approximately)
46 kilometers
25 nautical miles