The calculated distance (air line) between Kópavogur and Mosfellsbær is approximately 7 miles respectively 12 kilometers.
By car or train, the actual journey to Mosfellsbær is certainly longer, as only the direct route (as the crow flies) between Kópavogur and Mosfellsbær has been calculated here.
Air line (approximately)
12 kilometers
6 nautical miles