The calculated distance (air line) between Blois and Château-du-Loir is approximately 43 miles respectively 69 kilometers.
By car or train, the actual journey to Château-du-Loir is certainly longer, as only the direct route (as the crow flies) between Blois and Château-du-Loir has been calculated here.
Air line (approximately)
69 kilometers
37 nautical miles