The calculated distance (air line) between Loudun and Saint-Quentin-en-Yvelines is approximately 151 miles respectively 244 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 Loudun and Saint-Quentin-en-Yvelines has been calculated here.
Air line (approximately)
244 kilometers
131 nautical miles