Required PCB Trace Width for Current Calculator

Choosing PCB Trace Width for Current

When you know how much current a trace must carry, IPC-2221 can be inverted to estimate the minimum cross-section. Divide that area by copper thickness to get the required trace width.

Inverting the IPC-2221 Formula

$$A = \left(\frac{I}{k \times \Delta T^{0.44}}\right)^{1/0.725}$$ $$\text{width} = \frac{A}{\text{thickness}}$$

Use the same constants as the current calculator: $k = 0.048$ for external layers and $k = 0.024$ for internal layers. Results are starting points; add margin for manufacturing tolerance and derating.

Frequently Asked Questions

Should I use the exact calculated width?

Round up to the next practical fab width and leave margin. IPC values assume ideal conditions and a specific temperature rise.

Does impedance still matter for power traces?

Power traces are usually sized for current and voltage drop first. Signal nets may still need impedance control even if they are wider than a minimum current width.

Why is internal width larger for the same current?

Internal layers use a smaller IPC constant because heat escapes more slowly, so a larger cross-section is needed for the same temperature rise.

Can I use heavier copper instead of wider traces?

Yes. Thicker copper increases cross-section and can reduce required width, subject to fab capability and etching limits.

What if my load is pulsed?

IPC formulas assume continuous current. Short pulses may allow narrower traces, but thermal mass and duty cycle analysis are still required.

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PCB Trace Width Calculator

Choosing PCB Trace Width for Current

Inverting the IPC-2221 Formula

Frequently Asked Questions

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