The calculated distance (air line) between Pieksämäki and Lappeenranta is approximately 92 miles respectively 149 kilometers.
By car or train, the actual journey to Lappeenranta is certainly longer, as only the direct route (as the crow flies) between Pieksämäki and Lappeenranta has been calculated here.
Air line (approximately)
149 kilometers
80 nautical miles