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Trace Width

IPC-2221 or IPC-2152 — solve for required width or a trace's current capacity

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Solve for

Standard

Current

Trace width

mil

Temp rise

°C

Copper weight

Layer

Trace length

Required width

30.8 mil

Required width

0.781 mm

Cross-section

42.4 mil²

Resistance

32.1 mΩ

Voltage drop

64.1 mV

Dissipation

128 mW

Formula

A = {(\frac{I}{k \cdot {Δ T}^{b}})}^{1 / c}

W = \frac{A}{t \times 1.378}

Internal layers: k = 0.024, b = 0.44, c = 0.725

External layers: k = 0.048, b = 0.44, c = 0.725

I = current (A)
ΔT = allowed temperature rise (°C)
A = cross-section (mil²)
W = trace width (mil)
t = copper weight (oz); 1 oz of copper is 1.378 mil thick
k, b and c are curve-fit constants from IPC-2221's charts.

IPC-2221 is a conservative DC estimate for a bare trace in still air. Internal layers derate to roughly half the external current for the same geometry. Add margin for long runs, adjacent heat sources, and pulsed loads.