The calculated distance (air line) between Siltamäki and Lappeenranta is approximately 121 miles respectively 195 kilometers.
By car or train, the actual journey to Lappeenranta is certainly longer, as only the direct route (as the crow flies) between Siltamäki and Lappeenranta has been calculated here.
Air line (approximately)
195 kilometers
105 nautical miles