PCB analysis / Free calculator

PCB trace resistance

Estimate DC resistance, voltage drop, and power loss for a uniform copper trace.

01 Your inputs

Calculated on your device. Inputs are not transmitted or stored.

02 Your result

Enter your values and select Calculate.

Copper trace geometry

Plan view

Copper trace length, width, and current directionA straight copper strip sits on nonconducting board material. The length dimension follows the strip; w spans its width. Current I flows along the copper, not through the board.

Trace cross-section

Rectangular conducting area of the copper traceOnly the copper strip conducts. Its cross-section has width w and copper thickness t. The hatched material beneath is the board, not a return plane.

The copper rectangle is the conducting area A.

CopperBoard material
L
Trace length
w
Trace width
t
Copper thickness, not board thickness
Current travels along the trace. Its conducting area is width multiplied by copper thickness. Solder mask and surface finish are omitted. Symbolic model; not to scale.

The method

R=ρLAV=IRP=I2R

A worked example

A 100 mm × 1 mm × 35 µm trace at 20 °C has area 0.035 mm² and resistance approximately 49.26 mΩ. At 1 A, voltage drop is 49.26 mV and loss is 49.26 mW.

Assumptions & limits

Uniform copper with ρ₂₀ = 1.724 × 10⁻⁸ Ω·m and α = 0.00393/°C. The model accepts −100 to 300 °C; check whether the linear approximation is suitable at your temperature. Excludes self-heating, skin effect, pads, neck-downs, and manufacturing variation. Not an ampacity rating.

Calculation source: Extracted from PCBA Workbench v1.2.0; independent SI-unit reference tests.

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