The calculated distance (air line) between Blankenburg and Clausthal-Zellerfeld is approximately 26 miles respectively 42 kilometers.
By car or train, the actual journey to Clausthal-Zellerfeld is certainly longer, as only the direct route (as the crow flies) between Blankenburg and Clausthal-Zellerfeld has been calculated here.
Air line (approximately)
42 kilometers
23 nautical miles