Let's assume that your solar charge controller is 60A. Then multiply the solar controller's amps by the Average Battery Voltage for your size battery bank.

12V: 60A x 13.3V = ~800W
24V: 60A x 26.6V = ~1600W
36V: 60A x 39.9V = ~2400W
48V: 60A x 53.2V = ~3200W

If you have a PWM charge controller, then it's simply Amperage In = Amperage Out. Let's assume you have 1 string of solar panels tied to your charge controller with an Isc of 13A. Then 13A will be your PWM charge controller's output.

On the contrary, MPPT controllers use Power In = Power Out (less efficiencies). So to calculate output, then let's assume that your array's output is 80% (due to clouds, trees, etc.). Then...

Solary Array Watts x 0.80 = Power Out

Power Out / Average Battery Voltage = Amps Output

For example, for a 3000W solar array, let's assume you have a 48V battery bank.

3000W x 0.80 = 2400W

2400W / 53.2V = 45.11A output to the battery bank