How to Calculate PCB Trace Width?

PCB Trace Width Calculator







Designing a PCB requires careful consideration of the current-carrying capacity. If a trace is too narrow for a specific current, it will overheat, potentially damaging the board or causing system failure.

The IPC-2221 Standard The most common way to calculate the required width is using the IPC-2221 formula:

I=k⋅ΔTb⋅Ac

Where:

  • I is the current in Amperes.
  • ΔT is the temperature rise above ambient in °C.
  • A is the cross-sectional area of the trace in mils2.
  • k,b,c are constants derived from IPC curves.

Practical Tips for Engineers:

  1. Safety Margin: Always add a 20-30% margin to your calculated width to account for manufacturing tolerances.
  2. Copper Weight: Most standard PCBs use 1 oz/ft² (35 µm) copper thickness. For high-power applications, consider 2 oz/ft².
  3. Trace Placement: External traces (on the top or bottom layers) dissipate heat better than internal traces hidden in middle layers.
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