The calculated distance (air line) between Čáslav and Mladá Boleslav is approximately 41 miles respectively 66 kilometers.
By car or train, the actual journey to Mladá Boleslav is certainly longer, as only the direct route (as the crow flies) between Čáslav and Mladá Boleslav has been calculated here.
Air line (approximately)
66 kilometers
35 nautical miles