Free PCB Trace Width Calculator

Calculate minimum copper trace width, trace resistance, voltage drop, and power dissipation based on IPC-2221 and IPC-2152 standards.

⚡ Current & Board Specifications

Target Current (Amps) Continuous DC or RMS current

Copper Foil Weight

Allowable Temp Rise (ΔT)

Layer Location

Trace Length (Inches)

📊 Recommended Trace Geometry

Required Minimum Trace Width

68.4 mils

1.74 mm (0.068 inches)

Voltage Drop (IR)

0.043 V

Over 2.0" trace length

Power Dissipation (I²R)

0.130 Watts

Heat dissipated into PCB

Cross-Sectional Area: 93.7 sq mils (0.060 mm²)

Trace DC Resistance: 0.014 Ω (14.3 mΩ)

Copper Thickness (t): 1.37 mils (35.0 μm)

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Understanding IPC-2221 PCB Trace Sizing

As electric current flows through a PCB copper trace, electrical resistance ($R = ho cdot L / A$) generates heat ($P = I^2 R$). The trace heats up until thermal dissipation to ambient air and the FR-4 dielectric matches heat generation. Sizing according to IPC-2221 prevents delamination, solder reflow, and trace burning.

The IPC-2221 Formula

I = k \cdot (\Delta T)^{0.44} \cdot A^{0.725} \quad \longrightarrow \quad A = \left(\frac{I}{k \cdot (\Delta T)^{0.44}}\right)^{\frac{1}{0.725}}

\text{Where } k = 0.048 \text{ (External layers)}, \quad k = 0.024 \text{ (Internal layers)}

\text{Width (mils)} = \frac{A \text{ (sq mils)}}{t_{\text{copper}} \text{ (mils)}}

Why Internal Layers Need Twice the Width

External traces radiate heat directly to convective ambient air and cooling chassis fans. Internal traces on 4-layer and 6-layer boards are completely encapsulated in fiberglass-epoxy (FR-4), which acts as a thermal insulator. Internal traces run significantly hotter for the same current, requiring approximately double the cross-sectional area ($k = 0.024$).

Frequently Asked Questions

What is 1 oz copper in physical thickness?

1 oz copper means one ounce of copper rolled out evenly across a one square foot area. This yields an exact physical foil thickness of 1.37 mils (0.00137 inches, or 34.8 to 35.0 microns).

How do thermal vias under high-current traces help?

Stitching an array of solid ground/power vias beneath a high-current trace connects it to expansive inner plane layers, acting as a massive heat sink. This can easily double the safe ampacity of an external trace.

What temperature rise (Delta T) is standard?

For commercial consumer electronics operating in ambient rooms (25°C), an allowable temperature rise of 10°C to 20°C is standard, keeping peak board temperature well below the FR-4 glass transition temperature ($T_g \approx 130^\circ\text{C}$ to $170^\circ\text{C}$).