Electronics
PCB Trace Width Calculator
Enter the current a trace needs to carry, your acceptable temperature rise, copper weight, and whether the trace is on an external or internal layer, to get a minimum safe trace width.
Find the minimum copper trace width for a target current using the IPC-2221 model.
Based on the IPC-2221 external/internal trace formula. Add margin for real boards — thermal vias, nearby heat sources, and copper pour all shift the safe width.
IPC-2221 trace width model
Area = (I / (k · ΔT^0.44))^(1/0.725)
k is 0.048 for external layers and 0.024 for internal ones — internal traces need to be wider because they're surrounded by insulating substrate instead of open air, so they dissipate heat less efficiently.
How to use
- Enter the maximum current the trace will actually carry, not just the nominal or average current.
- Pick a temperature rise you're comfortable with — 10°C is a common conservative default; 20-30°C is more aggressive.
- Choose copper weight (1 oz/ft² is standard for most consumer boards) and whether the trace sits on an outer or inner layer.
Example
Input: 2A, 10°C rise, 1 oz copper, external layer
Output: ≈ 0.78 mm (30.8 mil) minimum width
Student-friendly breakdown
This walkthrough emphasizes the most searched ideas for PCB Trace Width Calculator: pcb trace width calculator, ipc-2221 calculator, trace width current calculator. Start with the formula above, then follow the guided steps to double-check your work. For quick revision, highlight the givens, plug into the equation, and finish by verifying your units.
Need more support? Use the links below to open the long-form guide, browse additional examples, or hop into adjacent calculators within the same topic — each one is a quick way to double-check your work or handle a related question without starting from scratch.
Deep dive & study plan
PCB Trace Width Calculator: Finds the minimum copper trace width for a target current using IPC-2221. It's built around pcb trace width calculator, ipc-2221 calculator, copper trace current calculator, so you can go from a raw question to a checked answer without switching tools.
The math behind it: k is 0.048 for external layers and 0.024 for internal ones — internal traces need to be wider because they're surrounded by insulating substrate instead of open air, so they dissipate heat less efficiently. The core relationship is Area = (I / (k · ΔT^0.44))^(1/0.725), shown above the calculator so you can see exactly how your inputs turn into the result.
To use it well: (1) Enter the maximum current the trace will actually carry, not just the nominal or average current. (2) Pick a temperature rise you're comfortable with — 10°C is a common conservative default; 20-30°C is more aggressive. (3) Choose copper weight (1 oz/ft² is standard for most consumer boards) and whether the trace sits on an outer or inner layer. Keep your units consistent as you go, and re-run a case you already know the answer to — it's the fastest way to catch a typo before it throws off a result you're relying on.
Worked example: entering 2A, 10°C rise, 1 oz copper, external layer returns ≈ 0.78 mm (30.8 mil) minimum width. Try swapping in your own numbers next, especially a case you're unsure about, before you use this for something that matters.
Quick retention checklist
- Speak the formula aloud (or annotate it) so the relationships stick.
- Write each step in your own words and compare with the numbered list above.
- Swap in new numbers for the Example to make sure the calculator (and your logic) handles edge cases.
- Check at least one related calculator below — it's the fastest way to confirm your numbers still line up from a different angle.
FAQ & notes
Should I just use the exact calculated width?
Treat it as a floor, not a target. Manufacturing tolerances, nearby heat sources, and long-term reliability all favor adding margin — many designers round up to the next standard width or add 20-30% headroom for anything carrying meaningful current.
Why does internal layer routing need a much wider trace for the same current?
External traces can shed heat directly into the air (and often get help from solder mask being thin); internal traces are sandwiched in fiberglass substrate, which is a much worse conductor of heat, so they need more copper cross-section to stay at the same temperature.
What formula does the PCB Trace Width Calculator use?
k is 0.048 for external layers and 0.024 for internal ones — internal traces need to be wider because they're surrounded by insulating substrate instead of open air, so they dissipate heat less efficiently.
How do I use the PCB Trace Width Calculator?
Enter the maximum current the trace will actually carry, not just the nominal or average current. Pick a temperature rise you're comfortable with — 10°C is a common conservative default; 20-30°C is more aggressive. Choose copper weight (1 oz/ft² is standard for most consumer boards) and whether the trace sits on an outer or inner layer.