What resistivity value is used for copper?

The calculator uses 1.72 × 10⁻⁸ Ω·m (17.2 nΩ·m), which is the standard IPC-2221 value for annealed copper at 20°C. A temperature coefficient of 0.00393 /°C adjusts the result to your operating temperature.

What is "copper weight" on a PCB?

Copper weight describes the thickness of the copper layer, expressed as weight per square foot. 1 oz copper corresponds to approximately 35 µm (1.378 mil) thick. 0.5 oz is about 17.5 µm and 2 oz is about 70 µm.

Why are width inputs in mils instead of millimeters?

Mils (thousandths of an inch) are the industry-standard unit for PCB trace widths in EDA tools like KiCad, Altium, and Eagle. 1 mil = 0.0254 mm. You can convert: mm × 39.37 = mils.

Does this include skin effect at high frequencies?

No — this calculator gives DC resistance only. At RF frequencies the effective cross-section shrinks due to skin effect, increasing AC resistance. For RF work use a dedicated skin-depth calculator.

How accurate is this calculation?

It is accurate to within a few percent for standard FR4 boards with plated-through copper. Real-world resistance may vary slightly due to plating uniformity, copper purity, and etch tolerances.

PCB Trace Resistance Calculator

Name: PCB Trace Resistance Calculator
Availability: InStock
Author: Nham Vu

Enter trace length, width, copper weight, and temperature to get the DC resistance of a PCB copper trace.

Trace Parameters

Trace Length (mm)

Trace Width (mils)

1 mil = 0.0254 mm. Typical signal trace: 6–10 mil; power trace: 20–100 mil.

Copper Weight

Operating Temperature (°C)

Reference temperature is 20°C. Typical operating range: −55°C to 125°C.

Results

Enter parameters and click Calculate.

Summary

Enter trace length, width, copper weight, and temperature to get the DC resistance of a PCB copper trace.

How it works

Enter the trace length in millimeters.
Enter the trace width in mils (thousandths of an inch, standard PCB unit).
Select the copper weight (thickness) — 0.5 oz, 1 oz, or 2 oz per square foot.
Optionally adjust the temperature (default 25°C).
The calculator applies R = ρL / (W × T) with a temperature coefficient correction and displays the resistance in milliohms.

Use cases

Verify power traces can handle the required current without excessive voltage drop.
Check that long ground return paths do not introduce significant resistance.
Estimate I²R heating in high-current sections of a PCB layout.
Compare 1 oz vs 2 oz copper options for cost vs resistance trade-off.
Validate that sense resistor bypass traces do not skew measurements.
Design low-resistance motor driver layouts for robotics and power electronics.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu