The calculated distance (air line) between L'Hospitalet de Llobregat and Granollers is approximately 20 miles respectively 32 kilometers.
By car or train, the actual journey to Granollers is certainly longer, as only the direct route (as the crow flies) between L'Hospitalet de Llobregat and Granollers has been calculated here.
Air line (approximately)
32 kilometers
17 nautical miles