The calculated distance (air line) between Saint-Quentin-en-Yvelines and Nanterre is approximately 12 miles respectively 19 kilometers.
By car or train, the actual journey to Nanterre is certainly longer, as only the direct route (as the crow flies) between Saint-Quentin-en-Yvelines and Nanterre has been calculated here.
Air line (approximately)
19 kilometers
10 nautical miles