The calculated distance (air line) between Frankfurt am Main and Kempten (Allgäu) is approximately 181 miles respectively 291 kilometers.
By car or train, the actual journey to Kempten (Allgäu) is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Kempten (Allgäu) has been calculated here.
Air line (approximately)
291 kilometers
157 nautical miles