The calculated distance (air line) between Estavayer-le-Lac and Sankt Gallen is approximately 125 miles respectively 202 kilometers.
By car or train, the actual journey to Sankt Gallen is certainly longer, as only the direct route (as the crow flies) between Estavayer-le-Lac and Sankt Gallen has been calculated here.
Air line (approximately)
202 kilometers
109 nautical miles