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TOOL IDB-ELE-010
PCB trace width

Desktop only

Engineering tools are available only on desktop screens.

PCB trace width

Minimum trace width to carry a given current at a given temperature rise per IPC-2221. Internal layers run hotter than external.

Cross-section — FR4 + copper w = —
FR-4 w 35 µm I = 2 A ΔT = 20 °C
Ampacity curve (IPC-2221) width vs current at fixed ΔT
— mm 0 0 A — A Current → Trace width → external internal
Engineering notes

Formula (IPC-2221A)

  • A [mil²] = (I / (k · ΔT^0.44))^(1/0.725)
  • External k = 0.048. Internal k = 0.024.
  • Width [mil] = A / (thickness [oz] · 1.378)

Practical adjustments

  • Add 50–100% margin near connectors, vias, and heat sources.
  • For >10 A, use copper pours, parallel traces, or bus bars.
  • Validate critical nets with thermal imaging.

Result

Live