The calculated distance (air line) between Belp and Zürich (Kreis 9) / Altstetten is approximately 58 miles respectively 93 kilometers.
By car or train, the actual journey to Zürich (Kreis 9) / Altstetten is certainly longer, as only the direct route (as the crow flies) between Belp and Zürich (Kreis 9) / Altstetten has been calculated here.
Air line (approximately)
93 kilometers
50 nautical miles