Engineering CalculatorsPCB Trace Width Calculator (IPC-2221)
Current-carrying capacity, required trace width, or resulting temperature rise for a PCB copper trace, from the IPC-2221 empirical model — plus first-principles trace resistance, voltage drop, and power dissipation.
New to IPC-2221? Read the guide: PCB Trace Width & Current Capacity: What IPC-2221 Actually Says — a plain-language explainer of the standard behind this calculator.
Current capacity, required trace width, and temperature rise come from the IPC-2221 (formerly IPC-D-275) empirical curve fit I = k·ΔT^0.44·A^0.725 (k = 0.048 external / 0.024 internal) — the same equation nearly every published PCB trace-width calculator implements. It's a curve fit to IPC's original thermal test data, not a first-principles derivation: modelling how a trace actually sheds heat (in-plane spreading through copper pours and plane layers, through-thickness conduction into FR4, heat paths out through connectors and vias) is a full 3-D FEA problem with no closed form — which is exactly why IPC's newer IPC-2152 standard, which refines the underlying test data for board thickness, adjacent plane layers, and trace length, publishes only charts rather than a formula. This tool computes from the disclosed IPC-2221 equation rather than transcribing unverifiable IPC-2152 chart readings. Trace resistance, voltage drop, and power dissipation are genuinely first-principles, using the same temperature-dependent copper resistivity model as the Busbar and Cable/Wire Sizing calculators. Treat this as a screening/estimation tool — for high-reliability designs, cross-check against your fab's process capability and, where available, IPC-2152 chart data or thermal simulation.
Validated: a 10 mil, 1 oz external trace at 10°C rise returns 0.88 A from the exact IPC-2221 equation — in the same range as the ~1 A figure commonly quoted as a rule of thumb for that exact case (rule-of-thumb roundings vary slightly by source; this tool always computes from the equation directly). All three solve directions (current/width/temperature rise) round-trip back to their inputs exactly, and an internal-layer trace of the same geometry returns exactly half the external layer's current capacity, as the k = 0.024 vs 0.048 constants require.