The calculated distance (air line) between Zürich (Kreis 9) / Altstetten and Sankt Gallen is approximately 42 miles respectively 67 kilometers.
By car or train, the actual journey to Sankt Gallen is certainly longer, as only the direct route (as the crow flies) between Zürich (Kreis 9) / Altstetten and Sankt Gallen has been calculated here.
Air line (approximately)
67 kilometers
36 nautical miles