The calculated distance (air line) between Veľký Krtíš and Piešťany is approximately 75 miles respectively 120 kilometers.
By car or train, the actual journey to Piešťany is certainly longer, as only the direct route (as the crow flies) between Veľký Krtíš and Piešťany has been calculated here.
Air line (approximately)
120 kilometers
65 nautical miles