The calculated distance (air line) between Bratislava - Vajnory and Piešťany is approximately 39 miles respectively 63 kilometers.
By car or train, the actual journey to Piešťany is certainly longer, as only the direct route (as the crow flies) between Bratislava - Vajnory and Piešťany has been calculated here.
Air line (approximately)
63 kilometers
34 nautical miles