The calculated distance (air line) between Frankfurt am Main and Louvain-la-Neuve is approximately 183 miles respectively 295 kilometers.
By car or train, the actual journey to Louvain-la-Neuve is certainly longer, as only the direct route (as the crow flies) between Frankfurt am Main and Louvain-la-Neuve has been calculated here.
Air line (approximately)
295 kilometers
159 nautical miles