I am designing a PCB for controlling servos.
My voltage regulator can provide 3 amps to the servos. My Arduino Uno also draws power from the same line. Using an online calculator, I was able to determine that I need 53 mil traces for power and ground lines coming directly from the regulator, and from devices powered by the regulator, respectively. Since the Arduino can draw at most about 500mA, I know that I don't need any special width for traces into and out of the Arduino's inputs and outputs.
The Arduino has its own voltage regulator, and a few ICs are powered by its 5V and 3.3V supplies.
Do I need 53 mil ground lines everywhere from these chips? Since the Arduino can't pump 3A, I can't imagine any one of these chips needing such a huge trace for ground lines.