The calculated distance (air line) between Terrassa and El Prat de Llobregat is approximately 17 miles respectively 27 kilometers.
By car or train, the actual journey to El Prat de Llobregat is certainly longer, as only the direct route (as the crow flies) between Terrassa and El Prat de Llobregat has been calculated here.
Air line (approximately)
27 kilometers
15 nautical miles