The calculated distance (air line) between Le Pecq and Saint-Quentin-en-Yvelines is approximately 9 miles respectively 15 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 Le Pecq and Saint-Quentin-en-Yvelines has been calculated here.
Air line (approximately)
15 kilometers
8 nautical miles