KiCad includes a calculator that you can use to precisely work out what the width of a track should be based on various parameters, like the current you wish to convey through the trace, its total length, and the maximum temperature rise when that current is actually flowing through it. You can use this calculator to find out the minimum trace width, or you can rely on your experience and choose a width that is much larger than the standard width of signal traces.

To use the calculator, open the KiCad launcher window and click on the calculator icon (Figure 26.1).

Figure 26.1:The calculator is available through the KiCad launcher window. The calculator app actually contains multiple calculators. One of them is the Track Width calculator. Select it by clicking on its tab. Fill in the values that best describe your power track requirements. For a typical Arduino gadget, the values that you see in Figure 26.2 are reasonable. I have only altered the conductor length value to 30mm to better match the power trace length of one of my PCB projects. I tend to overshoot these values to ensure that the trace width that the calculator returns can comfortably cover the requirements.

Figure 26.2:The Track Width calculator.

At the top right corner of the calculator, there is a field where you can provide the trace thickness. This is a value that you don’t have control over and is defined by the manufacturer’s specifications (some manufacturers allow you to select the weight of your copper trace, but for simplicity let’s assume here that this is fixed). The default value, 0.035 mm, seems to be an industry standard. Manufacturers typically make their boards with that trace thickness. To be sure, either search your preferred manufacturer’s website for their trace thickness or ask them.

As you type in the parameters, the calculator returns the suggested trace width. In the example of Figure 26.2, the suggested width is 0.30 mm.