The calculated distance (air line) between Ouderkerk aan de Amstel and Nijmegen is approximately 51 miles respectively 82 kilometers.
By car or train, the actual journey to Nijmegen is certainly longer, as only the direct route (as the crow flies) between Ouderkerk aan de Amstel and Nijmegen has been calculated here.
Air line (approximately)
82 kilometers
44 nautical miles