The calculated distance (air line) between Balsthal and Zürich (Kreis 3) is approximately 38 miles respectively 61 kilometers.
By car or train, the actual journey to Zürich (Kreis 3) is certainly longer, as only the direct route (as the crow flies) between Balsthal and Zürich (Kreis 3) has been calculated here.
Air line (approximately)
61 kilometers
33 nautical miles