The calculated distance (air line) between Niefern-Öschelbronn and Mannheim is approximately 42 miles respectively 68 kilometers.
By car or train, the actual journey to Mannheim is certainly longer, as only the direct route (as the crow flies) between Niefern-Öschelbronn and Mannheim has been calculated here.
Air line (approximately)
68 kilometers
37 nautical miles