The calculated distance (air line) between Cheboksary and Mariinskiy Posad is approximately 18 miles respectively 29 kilometers.
By car or train, the actual journey to Mariinskiy Posad is certainly longer, as only the direct route (as the crow flies) between Cheboksary and Mariinskiy Posad has been calculated here.
Air line (approximately)
29 kilometers
16 nautical miles