The calculated distance (air line) between Frankfurt am Main and Königstein im Taunus is approximately 10 miles respectively 17 kilometers.
By car or train, the actual journey to Königstein im Taunus is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Königstein im Taunus has been calculated here.
Air line (approximately)
17 kilometers
9 nautical miles