The calculated distance (air line) between Sauðárkrókur and Borgarnes is approximately 107 miles respectively 171 kilometers.
By car or train, the actual journey to Borgarnes is certainly longer, as only the direct route (as the crow flies) between Sauðárkrókur and Borgarnes has been calculated here.
Air line (approximately)
171 kilometers
93 nautical miles