The calculated distance (air line) between Frankfurt am Main and Bad Soden am Taunus is approximately 8 miles respectively 13 kilometers.
By car or train, the actual journey to Bad Soden am Taunus is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Bad Soden am Taunus has been calculated here.
Air line (approximately)
13 kilometers
7 nautical miles