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PCB Trace Width Calculator

Estimate a printed-circuit-board copper trace width from current, copper weight, layer position and allowed temperature rise—or estimate current for a known width.

Classic IPC-2221 empirical approximation: I = k × ΔT^0.44 × A^0.725; A is cross-sectional area in square mils, with k=0.048 external and 0.024 internal. This is not certification or a safety guarantee. It omits board stack-up, etching, plating, copper roughness, nearby planes, airflow, pulses, ambient temperature and manufacturing tolerances. Check the current applicable IPC standard and have real designs reviewed. The standard text may require purchase. Runs locally; no upload. IPC standards catalog

How do you estimate PCB trace width?

Choose a width or current-capacity estimate, select an internal or external copper layer, and enter current, copper weight and temperature rise. The calculator uses the classic IPC-2221 empirical equation and reports width in mil and millimetres.

Frequently asked questions

How do you estimate PCB trace width?

Choose a width or current-capacity estimate, select an internal or external copper layer, and enter current, copper weight and temperature rise. The calculator uses the classic IPC-2221 empirical equation and reports width in mil and millimetres.

Are my PCB values uploaded?

No. The estimate runs in this browser; values are not uploaded or saved.

What formula does this PCB trace calculator use?

It uses the classic IPC-2221 empirical relationship I = k × ΔT^0.44 × A^0.725, where current is in amperes, temperature rise is in °C, and cross-section is in square mils. The k value differs for external and internal traces.

Why does the estimate depend on whether the trace is internal or external?

The classic model uses different empirical constants for internal and external conductors. Real heat flow also depends on the board stack-up, copper planes, airflow and manufacturing, which this simple estimate does not model.

Is this a safe width or IPC-compliant design?

No. It is an approximate educational estimate, not certification or a safety guarantee. Use the current applicable standard, thermal analysis and qualified review for a real board. IPC lists IPC-2221 and IPC-2152 in its standards catalog.