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PCB Trace Width Calculator — IPC-2221 Current, Copper & Temperature Rise
Estimate PCB copper trace width and cross-sectional area from current, copper weight, allowed temperature rise and external/internal layer position using the IPC-2221 empirical relationship.
Last updated: September 16, 2026
Results
Required width 11.82584 mil
Required width 0.3003762 mm
Cross-section 16.296 mil²
Formula, example and assumptions
I=k·ΔT^0.44·A^0.725; width=A/thickness.
1 A on 1 oz external copper with 10 °C rise needs roughly 12 mil by the IPC-2221 curve.
- IPC-2221 is an empirical planning model, not a complete thermal simulation.
- Vias, planes, airflow, ambient temperature and fabrication tolerance can materially change temperature.
Frequently asked questions
Why are internal traces wider?
Buried traces shed heat less effectively, so the IPC-2221 internal-layer coefficient is lower.
Does this replace PCB thermal validation?
No. Use it for first-pass sizing and validate critical designs against current IPC guidance, stackup and measurements.