The calculated distance (air line) between Mstera and Nizhniy Novgorod is approximately 80 miles respectively 128 kilometers.
By car or train, the actual journey to Nizhniy Novgorod is certainly longer, as only the direct route (as the crow flies) between Mstera and Nizhniy Novgorod has been calculated here.
Air line (approximately)
128 kilometers
69 nautical miles