Free PCB Tool · IPC-2221
PCB Trace Width Calculator
Enter your current, copper weight and allowed temperature rise. Get the minimum trace width instantly — using the IPC-2221 standard formula, the same one professional EDA tools apply.
Cross-section 42.4 mil²
Quick reference
Handy tables for laying out a board — no login, no paywall.
Copper weight → thickness
| Weight | Thickness | µm |
|---|---|---|
| 0.5 oz | 0.689 mil | 17.5 |
| 1 oz | 1.378 mil | 35 |
| 2 oz | 2.756 mil | 70 |
| 3 oz | 4.134 mil | 105 |
Common drill sizes
| Use | Drill | Pad |
|---|---|---|
| Via (std) | 0.3 mm | 0.6 mm |
| Via (fine) | 0.2 mm | 0.45 mm |
| 0.1" header | 1.0 mm | 1.8 mm |
| M2 mount | 2.2 mm | — |
| M3 mount | 3.2 mm | — |
Typical trace / space
| Class | Min trace | Min space |
|---|---|---|
| Hobby / cheap | 6 mil | 6 mil |
| Standard | 5 mil | 5 mil |
| Advanced | 4 mil | 4 mil |
| HDI | 3 mil | 3 mil |
Layer stackups
| Layers | Typical use |
|---|---|
| 2 | Simple, low-speed |
| 4 | Sig / GND / PWR / Sig |
| 6 | Mixed-signal, RF |
| 8+ | SBC, DDR, dense BGA |
How the calculation works
IPC-2221, in plain terms.
The IPC-2221 formula
Required cross-sectional area (in mil²): A = ( I / (k × ΔT0.44) )1/0.725, where I is current in amps, ΔT is the allowed temperature rise in °C, and k = 0.048 for external layers or 0.024 for internal layers. Width = area ÷ copper thickness (in mils).
Why internal traces need to be wider
Internal layers are buried in the board and shed heat far less efficiently than the outer copper, so IPC-2221 halves the constant (k = 0.024). For the same current and temperature rise, an internal trace ends up roughly twice as wide as an external one.
Do I have to do this by hand for every net?
No. This page gives you a single width, but a real board has dozens of nets, each with its own current and impedance target. An autorouter applies the correct width and spacing per net across every layer. PCBEditor is a free, browser-based PCB tool that does exactly that — describe the board and it places and routes it for you.
Skip the math — route the whole board
PCBEditor turns a plain-English description into a placed, routed, DRC-clean board in your browser. Free to try, no install.
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