The calculated distance (air line) between Frankfurt am Main and Marche-en-Famenne is approximately 148 miles respectively 238 kilometers.
By car or train, the actual journey to Marche-en-Famenne is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Marche-en-Famenne has been calculated here.
Air line (approximately)
238 kilometers
129 nautical miles