PCB Trace Width Calculator (IPC-2221)

Enter current, copper weight, and allowed temperature rise to get a recommended trace width for external or internal PCB layers. Includes unit conversions and Show Work.

How to Use

  1. Enter the current the trace must carry.
  2. Choose layer type (external or internal) and your copper weight.
  3. Set an allowed temperature rise (ΔT) for the trace.
  4. (Optional) Enter trace length to estimate resistance + voltage drop.
  5. Open Show Work to see the IPC-2221 steps and conversions.
Trace Lab View
Recommended width + quick checks based on IPC-2221.
Width
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Area
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ΔT
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I
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Advisory: —
FR-4 (illustrative) Copper Recommended width: — Copper weight: — Layer: — Visual is illustrative; final design should consider plane proximity, airflow, vias, pours, and IPC-2152 guidance.
Inputs & Settings
IPC-2221 width estimate from current, copper, ΔT, and layer type.
Enter the continuous current your trace must carry.
Typical design choices: 10°C to 20°C rise.
Internal traces generally require more area for the same current/ΔT.
Common: 0.5oz, 1oz, 2oz. Tool converts to thickness.
Used only to estimate resistance + voltage drop (optional).
Leave blank to use a standard copper value for estimates.
Show Work (step-by-step)
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Work is shown using consistent base units. IPC-2221 equations are empirical; real boards can vary.

Reference

This tool uses the classic IPC-2221 approach relating current, temperature rise, and conductor cross-sectional area. Many designers also consult IPC-2152 for more modern guidance, especially for complex stackups and thermal conditions.

  • Inputs: Current (I), allowed rise (ΔT), copper thickness/weight, layer type
  • Outputs: Recommended width, cross-sectional area, thickness conversions
  • Optional estimates: Resistance and voltage drop from length + copper resistivity
Always validate against your fab capabilities, minimum trace/space rules, and thermal environment.

FAQ

External vs internal: why different?

External traces shed heat more easily to air and surrounding copper, so they often need less cross-sectional area than internal traces for the same current and ΔT.

What copper weight should I pick?

1oz is common for signals and light power. 2oz (or more) is used when you need higher current without very wide traces. This tool converts oz/ft² to thickness for calculations.

Is IPC-2221 always accurate?

It’s a useful baseline but empirical. Thermal performance depends on stackup, pours, vias, airflow, and nearby copper. Consider IPC-2152-style validation for critical power designs.

Why do you round widths?

Rounding helps land on practical CAD/fab-friendly values. You can disable rounding if you want the raw computed width.

Tool Info

Last updated:

Updates may include improved rounding options, better warnings, and expanded export formatting.