The calculated distance (air line) between Międzyrzec Podlaski and Białystok is approximately 81 miles respectively 130 kilometers.
By car or train, the actual journey to Białystok is certainly longer, as only the direct route (as the crow flies) between Międzyrzec Podlaski and Białystok has been calculated here.
Air line (approximately)
130 kilometers
70 nautical miles