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PCB Trace Width Calculator

Estimate the minimum copper trace width for a current and allowed temperature rise using the IPC-2221 model.

01

INPUTS

A

Continuous current carried by the trace.

°C

Allowed conductor temperature rise above ambient.

oz

Copper thickness in ounces per square foot.

External layers dissipate heat better, so they need less copper than internal layers.

02

RESULT

Minimum width

Minimum trace width

11.8 mils

≈ 0.300 mm

Calculation summary

Cross-sectional area
16.30 mils²
Trace width
0.300 mm
Layer
External
Copper weight
1 oz

Calculation trace

  1. 1 A ÷ (k · ΔT^0.44)
    = 16.30 mils²
    Cross-section (IPC-2221)
  2. 16.30 mils² ÷ (1 oz × 1.378)
    = 11.8 mils
    Trace width
  3. 11.83 mils × 0.0254
    = 0.300 mm
    Millimetres

Notes

  • Based on the IPC-2221 empirical model. Verify against your board house and derate for long traces, vias and dense areas.
03

HOW IT WORKS

About this calculationThe IPC-2221 current-capacity model.

IPC-2221 relates the copper cross-sectional area to current and temperature rise. Dividing the required area by the copper thickness (weight × 1.378 mils/oz) gives the trace width.

Assumptions & limitationsEmpirical, bounded model.
  • Empirical curves, roughly valid to 35 A and 100 °C rise.
  • No derating for vias, pads, dense areas or long runs.
  • Verify against your board house before manufacturing.
Example scenariosSee how the layer changes the width.
  • 3 A · 10 °C rise · 1 oz · external: 53.8 mils
  • 3 A · 10 °C rise · 1 oz · internal: 140.0 mils
04

SOURCES & REVIEW

Source records
Method version pcb-ipc2221@1.0.0-provisional. IPC-2221 generic-standard empirical model.
Review status
Provisional; not independently reviewed. Not indexed until sourced.
Report an issue
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05

RELATED TASKS

Size a via
Via Current Capacity Calculator — coming soon.
Pick a copper weight
Copper Weight Calculator — coming soon.
Check current capacity
Trace Current Calculator — coming soon.