The calculated distance (air line) between San Luis Potosí and Guanajuato is approximately 80 miles respectively 129 kilometers.
By car or train, the actual journey to Guanajuato is certainly longer, as only the direct route (as the crow flies) between San Luis Potosí and Guanajuato has been calculated here.
Air line (approximately)
129 kilometers
70 nautical miles