The calculated distance (air line) between Pieksämäki and Seinäjoki is approximately 141 miles respectively 227 kilometers.
By car or train, the actual journey to Seinäjoki is certainly longer, as only the direct route (as the crow flies) between Pieksämäki and Seinäjoki has been calculated here.
Air line (approximately)
227 kilometers
123 nautical miles