The calculated distance (air line) between Saint-Leu-la-Forêt and Écouen is approximately 6 miles respectively 10 kilometers.
By car or train, the actual journey to Écouen is certainly longer, as only the direct route (as the crow flies) between Saint-Leu-la-Forêt and Écouen has been calculated here.
Air line (approximately)
10 kilometers
5 nautical miles