PCB Trace Width Calculator

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External traces dissipate heat to the surrounding air and can carry more current at a given width. Internal traces are embedded in FR4 and run hotter for the same current.
The maximum continuous current the trace must carry.
A
How many degrees Celsius the trace is allowed to rise above ambient. 10 °C is a common conservative value; up to 40 °C is acceptable in many applications.
°C
1 oz copper equals a 1.37 mil (35 μm) thick layer. Heavier copper allows narrower traces for the same current but increases board cost.
Physical length of the trace on the PCB. Used to calculate resistance, voltage drop, and power loss.
mm
Operating environment temperature. Affects copper resistivity and the copper temperature coefficient correction.
°C
Add extra width beyond the calculated minimum. A 20% margin is common practice to account for manufacturing tolerances and derating.
%
Min. trace widthStandard trace
14.27mils

Minimum required trace width including your safety margin (IPC-2221)

Min. trace width0.363mm
Raw min. width (no margin)11.89mils
Trace resistance0.0697Ω
Trace resistance69.67mΩ
Voltage drop0.0697V
Power dissipated0.0697W
Max. trace temperature35°C
Cross-section area19.56mils²
14.27 mils
Very fine<5Standard5-50Heavy50-150Power trace150+

Minimum trace width: 14.27 mils (0.363 mm)

  • The IPC-2221 minimum trace width for 1 A on an external layer is 11.89 mils (0.302 mm). With your 20% safety margin the recommended width is 14.27 mils (0.363 mm).
  • At 1 A the trace drops 69.67 mV and dissipates 69.67 mW. For most logic supplies a drop under 50 mV is acceptable; for power rails budget accordingly.

Next stepRound the calculated width up to the nearest 5 mil or manufacturer grid step before committing to your layout. Always verify the result against your fab house design rules.

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