The calculated distance (air line) between Blois and Montlouis-sur-Loire is approximately 27 miles respectively 44 kilometers.
By car or train, the actual journey to Montlouis-sur-Loire is certainly longer, as only the direct route (as the crow flies) between Blois and Montlouis-sur-Loire has been calculated here.
Air line (approximately)
44 kilometers
24 nautical miles