The calculated distance (air line) between Burg auf Fehmarn and Grevesmühlen is approximately 39 miles respectively 63 kilometers.
By car or train, the actual journey to Grevesmühlen is certainly longer, as only the direct route (as the crow flies) between Burg auf Fehmarn and Grevesmühlen has been calculated here.
Air line (approximately)
63 kilometers
34 nautical miles