Trace Width Calculator
Estimate trace width from current, temperature rise and copper weight using the IPC-2221 approximation.
Size your trace
Enter the expected current, allowable temperature rise and copper weight. The result follows the IPC-2221 chart approximation and adds a 20% margin.
This is a starting point for layout, not a substitute for thermal simulation. For high-current, high-reliability or sealed designs, ask us for a stack-up review.
IPC-2221 in plain terms
For a given current, allowable temperature rise and copper thickness, the required conductor cross-section is calculated, then divided by copper thickness to give a minimum trace width. Internal layers run hotter for the same current because laminate conducts heat away less effectively, so the calculator applies a different constant.
| Variable | What it means in practice |
|---|---|
| Current (A) | Use the maximum continuous current, plus any transient overload your product must survive. |
| Temperature rise (°C) | 10 °C is a common conservative target; 20–30 °C is often used where board space is tight. |
| Copper weight | 1 oz ≈ 35 µm. Heavier copper reduces width but changes etch and assembly constraints. |
| Layer type | External traces cool through air; internal traces are surrounded by laminate and need more width. |
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