PCB Trace Width Calculator (IPC-2221)
Current vs trace width vs temp rise
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PCB Trace Width Calculator (IPC-2221A)
Calculate minimum PCB trace width for given current + allowed temperature rise. Per IPC-2221A standard. External vs internal layers, copper weight 0.5/1/2/3 oz.
How to use this tool
- 1
Current + temp rise
Trace current and allowed Δt.
- 2
Copper weight + layer
1oz/2oz, internal vs external.
- 3
Min trace width
Per IPC-2221A formula.
Frequently Asked Questions
IPC-2221A formula?
I = k × ΔT^0.44 × A^0.725. External: k = 0.048; internal: k = 0.024. ΔT in °C, A in mil² (cross-section), I in amps. Solved for required area.
Why are internal traces worse?
No air convection — heat trapped. Same trace width carries ~half the current vs external. Internal layers always need ~2× wider for same current.
1oz vs 2oz copper?
1oz = 35 µm thick, 2oz = 70 µm. 2oz roughly halves required width (more cross-section). Cost: 2oz costs ~30% more, used for power-handling boards.
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