PCB Trace Width Calculator (IPC-2221) – Current vs Temperature Rise
Traces heat up as current flows. IPC-2221 gives an empirical fit between current, cross-sectional area and temperature rise. External layers cool better than internal ones, so they can be narrower.
A
= 1 A°C
mm
°C
Results
- Minimum width
- 0.3 mm (11.8 mil)
- Cross-section
- 16.3 mil²
- Copper thickness
- 35 µm
- Trace resistance
- 86.62 mΩ
- Voltage drop
- 86.62 mV
- Power loss
- 86.62 mW
Pro
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Minimum width: 0.3 mm (11.8 mil)
Formula
- I = k · ΔT^0.44 · A^0.725 (A in mil²)
- k = 0.048 external, 0.024 internal
- W = A / (t · 1.378 mil/oz)
FAQ
- Is IPC-2221 conservative?
- Generally yes, especially for internal layers. The newer IPC-2152 uses more detailed data. Treat this as a safe starting point.
- What temperature rise should I choose?
- 10 °C is a common default. Allow more only if you know the board and components can tolerate it.