Trace Width
11.6 mils
mm
0.296 mm
Area
16.3 mil²
Minimum Trace Width
11.6 mils
0.296 mm
Cross-Section
16.3 mil²
Standard
IPC-2221
I = k × ΔT⁰ˢ⁴⁴ × A⁰ˢ⁷²⁵
Inputs
Result
A = (1/(0.048×10^0.44))^(1/0.725) = 14.3 mil². Width = 14.3/1.4 = 10.2 mils.
Inputs
Result
A = (3/(0.048×10^0.44))^(1/0.725) = 37.2 mil². Width = 37.2/2.8 = 13.3 mils.
IPC-2221: I = k × ΔT^0.44 × A^0.725. Solve for area A, then width = A/thickness. For 1A on external 1oz copper with 10°C rise: width ≈ 10.2 mils (0.26mm).
| Current | 1oz External | 1oz Internal | 2oz External |
|---|---|---|---|
| 0.5A | 5 mils | 8 mils | 3 mils |
| 1A | 10 mils | 17 mils | 5 mils |
| 3A | 26 mils | 50 mils | 13 mils |
| 5A | 40 mils | 80 mils | 20 mils |
10°C is conservative and standard. 20°C acceptable for most boards. 45°C maximum per IPC-2221. Higher rise = narrower trace but hotter board.
External traces dissipate heat to air; internal traces are insulated by FR4. IPC uses k=0.048 external, k=0.024 internal. Internal traces need roughly 2x the width for the same current.
1oz copper = 1.4 mils (35µm) thick. 2oz = 2.8 mils. Thicker copper needs narrower traces for the same current since cross-section area = width × thickness.
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Last Updated: Mar 20, 2026
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