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PCB Trace Width Calculator (IPC-2221)

Calculate minimum PCB copper trace width to safely carry a specified current with a given temperature rise, per IPC-2221 standard for external and internal traces.

Typical: 10�C for signal, 20�30�C for power traces. Lower = wider trace.
Standard PCBs use 1 oz copper. 2 oz for high-current applications.
Internal traces have less heat dissipation � require wider traces for same current.

Results

Trace Width (mils)11.8 mils
Trace Width (mm)0.300 mm

📖What is it?

The IPC-2221 standard defines minimum PCB trace widths for given current carrying capacity. The formula relates current to cross-sectional area: I = k � ?T^0.44 � A^0.725, where k = 0.048 (external) or 0.024 (internal), ?T = temperature rise, A = cross-section in mils�. Width = A / (copper thickness in mils). 1 oz copper = 1.378 mils thick.

🎯How to use

Enter the maximum current the trace will carry, the acceptable temperature rise above ambient, copper weight, and whether it is an external or internal trace. The minimum trace width is returned in both mils and millimeters.

💡Example scenario

1A, 10�C rise, 1oz copper, external trace: crossSection = (1/(0.048 � 10^0.44))^(1/0.725) = (1/0.138)^1.379 � 31.4 mil�. Width = 31.4/1.378 � 22.8 mils � 0.58 mm. Always add 20�30% margin ? use =0.75 mm.

🏆Pro tip

IPC-2221 is conservative and assumes a 25�C ambient in still air. For power supplies, motor drivers, and battery chargers, always add significant margin (50�100%) and consider copper pours instead of traces. Use vias to carry current between layers. Online tools like Saturn PCB Toolkit offer more refined calculations including via current capacity.