If you use a different CT sensor or resistor than in the tutorials, the best approach is to calibrate the system.
I do that by placing the CT sensor over one wire to an AC socket, and plug in various known wattage loads, like a 100 Watt light bulb, a 1000 W room heater, etc. Then observe the Arduino output and calculate a "best fit" scale factor.
Excellent tutorial on sensor calibration at Adafruit.