PCB Trace Width Calculator
Calculate the minimum PCB copper trace width for a given current and allowable temperature rise using the IPC-2221 formula, plus the trace's resistance, voltage drop, and power loss for a given length.
Input
10°C is a common default; higher allows a narrower trace.
Leave blank to skip the resistance, voltage drop, and power loss estimate.
Output
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/pcb-trace-width-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"current": "2",
"tempRise": "10",
"location": "external",
"copperWeight": "1",
"length": "100"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `pcb-trace-width-calculator` tool (PCB Trace Width Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/pcb-trace-width-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="PCB Trace Width Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
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Guides
The PCB Trace Width Calculator works out the minimum copper trace width needed to carry a given current without exceeding a target temperature rise, using the IPC-2221 current-capacity formula — the standard reference for PCB designers sizing traces. It also reports the trace's resistance, voltage drop, and power loss when you give it a trace length, so you can check both current-carrying capacity and signal/power integrity in one pass.
How to use it
- Enter the current the trace needs to carry, in amps.
- Enter the allowable temperature rise above ambient — 10°C is a common conservative default.
- Choose whether the trace is on an external (outer) or internal layer — internal traces need to be wider, since they can't dissipate heat as easily.
- Pick the copper weight (thickness), usually 1oz/ft² for standard boards, 2oz+ for higher-current designs.
- Optionally enter a trace length to also see resistance, voltage drop, and power loss.
Results update instantly: the required cross-sectional area, the copper thickness, the minimum trace width in mils and millimetres, and — when a length is given — the trace's resistance, voltage drop, and power dissipation. A full step-by-step derivation is included.
What is the IPC-2221 formula?
It's an empirical formula from the IPC-2221 PCB design standard relating a trace's cross-sectional area to the current it can carry for a given temperature rise: A = (I / (k × ΔT^0.44))^(1/0.725), where k is 0.048 for external traces and 0.024 for internal traces (internal traces run hotter for the same current since they're insulated by the board material on both sides).
Why does copper weight matter?
Copper weight (oz/ft²) sets the trace's thickness — 1oz/ft² is about 1.378 mils (35 µm) thick. Since the required width is the cross-sectional area divided by thickness, doubling the copper weight roughly halves the trace width needed for the same current.
How is voltage drop calculated?
Once a trace length is given, resistance follows R = ρL/A using copper's resistivity (ρ ≈ 1.72 × 10⁻⁸ Ω·m), then voltage drop is I × R and power loss is I² × R. Long, high-current traces can drop enough voltage to matter — this is the same reason wall-wart and battery leads are sized generously.
Is my data private?
Completely. Every calculation runs entirely in your browser. Nothing you type is uploaded, stored, or sent to a server.
For a general resistor/voltage/current relationship, see the Ohm's Law Calculator; for wiring runs rather than PCB traces, see the Voltage Drop Calculator.