PCB Trace Width

IPC-2221 sizes a trace from the current it carries and how much self-heating you accept: A = (I / (k·ΔT^0.44))^1/0.725, then width = area ÷ copper thickness. External traces run cooler than buried ones, so they can be narrower.

IPC-2221 is a conservative, decades-old curve. For dense or high-current boards confirm with a thermal check and your fabricator.