Typically the utility will give you the available fault current at the secondary terminals of the transformer that supplies the service. If that number is lower than the short circuit rating of the equipment, I just mark that number as the available fault current on the equipment.
If the number from the utility is close to, or higher than the equipment rating, you can do the calcs to see how much the impedance of the wire run has reduced the available fault current at the line side of your service equipment.
Bussmann has a nice app that will do the calculations.