The calculated distance (air line) between Ouderkerk aan de Amstel and Dordrecht is approximately 35 miles respectively 56 kilometers.
By car or train, the actual journey to Dordrecht is certainly longer, as only the direct route (as the crow flies) between Ouderkerk aan de Amstel and Dordrecht has been calculated here.
Air line (approximately)
56 kilometers
30 nautical miles