The calculated distance (air line) between Kópavogur and Reykjanesbær is approximately 21 miles respectively 34 kilometers.
By car or train, the actual journey to Reykjanesbær is certainly longer, as only the direct route (as the crow flies) between Kópavogur and Reykjanesbær has been calculated here.
Air line (approximately)
34 kilometers
18 nautical miles