The calculated distance (air line) between Veľký Krtíš and Lučenec is approximately 17 miles respectively 27 kilometers.
By car or train, the actual journey to Lučenec is certainly longer, as only the direct route (as the crow flies) between Veľký Krtíš and Lučenec has been calculated here.
Air line (approximately)
27 kilometers
15 nautical miles