PCB Trace Resistance Calculator

A PCB trace is the thin copper path on a circuit board that carries electrical current — and even small traces have measurable resistance that affects circuit performance. Enter your trace length, width, thickness, and temperature into the PCB Trace Resistance Calculator to get the trace resistance in ohms. Optionally, enter a current value to also see voltage drop and power dissipation along the trace.

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Enter current to calculate voltage drop

Results

Trace Resistance

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Resistance per Unit Length

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Voltage Drop

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Power Dissipation

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Frequently Asked Questions

How is PCB trace resistance calculated?

PCB trace resistance is calculated using the formula: R = ρ × (L / (T × W)) × (1 + α × (T_amb - 25°C)), where ρ is resistivity, L is length, T is thickness, W is width, α is temperature coefficient, and T_amb is ambient temperature.

What factors affect PCB trace resistance?

The main factors are trace length (longer = higher resistance), width (wider = lower resistance), thickness (thicker = lower resistance), temperature (higher temp = higher resistance), and material resistivity (copper has low resistivity).

Why does temperature affect trace resistance?

Copper has a positive temperature coefficient, meaning its resistance increases with temperature. The standard reference is 25°C, and resistance increases by approximately 0.39% per degree Celsius above this temperature.

How do I minimize PCB trace resistance?

To minimize resistance: use wider traces, shorter routing paths, thicker copper (higher oz/ft²), keep operating temperature low, and use multiple parallel traces for high-current applications.

What is the relationship between trace resistance and voltage drop?

Voltage drop across a trace equals the current multiplied by the trace resistance (V = I × R). Higher resistance or current results in greater voltage drop, which can affect circuit performance.

What copper thickness should I use for my PCB?

Standard PCBs use 1 oz/ft² (35µm) copper. Use 2 oz/ft² (70µm) or thicker for high-current applications. Thicker copper reduces resistance but increases manufacturing cost.

When is trace resistance important in PCB design?

Trace resistance is critical for power supply traces, high-current paths, precision analog circuits, and long traces. It affects voltage regulation, power efficiency, and signal integrity.