The calculated distance (air line) between San Ildefonso and Fuencarral-El Pardo is approximately 31 miles respectively 51 kilometers.
By car or train, the actual journey to Fuencarral-El Pardo is certainly longer, as only the direct route (as the crow flies) between San Ildefonso and Fuencarral-El Pardo has been calculated here.
Air line (approximately)
51 kilometers
27 nautical miles