The calculated distance (air line) between Château-Thierry and Saint-Quentin-en-Yvelines is approximately 66 miles respectively 106 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 Château-Thierry and Saint-Quentin-en-Yvelines has been calculated here.
Air line (approximately)
106 kilometers
57 nautical miles