The calculated distance (air line) between Niefern-Öschelbronn and Leonberg is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Leonberg is certainly longer, as only the direct route (as the crow flies) between Niefern-Öschelbronn and Leonberg has been calculated here.
Air line (approximately)
21 kilometers
12 nautical miles