The calculated distance (air line) between Montemor-o-Novo and Sesimbra is approximately 50 miles respectively 80 kilometers.
By car or train, the actual journey to Sesimbra is certainly longer, as only the direct route (as the crow flies) between Montemor-o-Novo and Sesimbra has been calculated here.
Air line (approximately)
80 kilometers
43 nautical miles