The calculated distance (air line) between Korsun-Shevchenkivskyy and Poltava is approximately 149 miles respectively 239 kilometers.
By car or train, the actual journey to Poltava is certainly longer, as only the direct route (as the crow flies) between Korsun-Shevchenkivskyy and Poltava has been calculated here.
Air line (approximately)
239 kilometers
129 nautical miles