PCB Trace Width
Calculate the minimum PCB copper trace width required to safely carry a specified current without exceeding a given temperature rise. This calculator implements the IPC-2221 standard the globally accepted industry benchmark for printed circuit board design. Supports both internal and external layer calculations.
IPC-2221 trace width
Required width30.8 mil
In millimetres0.78 mm
Cross-section42.4 mil²
StandardIPC-2221 external layer
Formulas used
IPC-2221: Area (mil²) = [I ÷ (k × ΔTb)]1/c → Width = Area ÷ (Thickness × 1.378)
How to use this calculator
Step-by-Step Instructions
- Enter the maximum current The highest continuous current the trace must carry, in Amps.
- Set allowable temperature rise 10°C is standard. Higher rises allow narrower traces but increase board temperature. Never exceed 30°C for most applications.
- Select copper thickness Most standard PCBs use 1oz copper (35µm). High-current boards may use 2oz or 3oz.
- Select layer type External layers dissipate heat better than internal layers, allowing narrower traces for the same current.
- Click Calculate The minimum trace width is shown in mils (thousandths of an inch) and millimeters.
Worked Example
Carrying 2A on external 1oz copper with 10°C rise:
Minimum trace width ≈ 25 mil (0.635mm) round up to 30 mil for safety margin.
Pro Tips
- Always add at least 20% safety margin to the calculated trace width for production reliability.
- Internal layers need approximately 2× wider traces than external layers for the same current capacity.
- For power supply traces carrying more than 5A, consider using copper pours (planes) instead of traces.