Electronics

PCB Trace Width Guide

PCB trace width for current capacity (IPC-2221) across copper weights and temperature rises.

Updated Apr 19, 2026 2 min read

External (outer) layer figures — doubled for internal layers because no air cooling. All values at 1 oz copper, 25 °C ambient.

10 °C rise

Current0.5 oz1 oz2 oz
1 A20 mil10 mil5 mil
2 A50 mil25 mil13 mil
3 A90 mil45 mil23 mil
5 A180 mil90 mil45 mil
10 A450 mil225 mil113 mil
15 A800 mil400 mil200 mil

20 °C rise

Current0.5 oz1 oz2 oz
1 A15 mil7 mil4 mil
2 A35 mil18 mil9 mil
3 A60 mil30 mil15 mil
5 A120 mil60 mil30 mil
10 A300 mil150 mil75 mil

30 °C rise

Current0.5 oz1 oz2 oz
1 A12 mil6 mil3 mil
2 A25 mil13 mil7 mil
3 A45 mil23 mil12 mil
5 A100 mil50 mil25 mil
10 A240 mil120 mil60 mil

Notes

  • IPC-2221 formula: I = k · ΔT^0.44 · A^0.725 where A = trace CSA in mil², k = 0.048 (external) / 0.024 (internal).
  • Design for the lowest expected ambient and worst-case current. Add pours / copper fills around power traces for spreading.
  • Convert: 1 oz copper ≈ 1.37 mil / 35 µm thick.
Was this article helpful?