PCB Trace Resistance Calculator

Category: Technology
- May 09, 2025
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Calculate the resistance, voltage drop, and power dissipation of PCB traces based on physical dimensions, copper weight, and current requirements.

Trace Dimensions

Typical PCB trace widths: 0.15-3mm (6-120mil)
Standard values: 0.5oz, 1oz, 2oz, 3oz
°C
Affects resistivity (20°C is reference)

Electrical Parameters

A
Leave at 0 to ignore voltage drop/power calculations
Surface finish affects conductivity

Advanced Options

Copper at 20°C: 1.68 μΩ·cm
Copper: 0.00393 per °C

PCB Trace Resistance Theory

The resistance of a PCB trace depends on its physical dimensions, the resistivity of copper, and the operating temperature. Understanding these factors is essential for designing power distribution networks and signal integrity in electronic circuits.

Key Factors Affecting Trace Resistance
  • Trace Length: Resistance increases linearly with length
  • Trace Width: Resistance decreases as width increases
  • Copper Thickness: Thicker copper (higher oz) reduces resistance
  • Temperature: Resistance increases with temperature (approx. 0.393% per °C for copper)
  • Surface Finish: Different plating types can affect the overall resistance
Resistance Calculation
  • Basic Resistance Formula: R = ρ × L / A
  • Where R is resistance in ohms (Ω)
  • ρ (rho) is the resistivity of copper (1.68 × 10-8 Ω·m at 20°C)
  • L is the trace length in meters
  • A is the cross-sectional area in square meters (width × thickness)
Temperature Effects
  • Temperature Coefficient: α = 0.00393 per °C for copper
  • Temperature Adjusted Resistance: R(T) = R(20°C) × [1 + α × (T - 20)]
  • Where T is the operating temperature in °C
Design Considerations
  • Voltage Drop: V = I × R (important for power traces)
  • Power Dissipation: P = I² × R (causes temperature rise)
  • Signal Integrity: High-frequency signals require transmission line analysis beyond DC resistance
  • Return Paths: Ground plane impedance should be minimized
  • Thermal Management: Consider heat dissipation for high-current traces

Disclaimer: This calculator provides estimates based on theoretical formulas for DC resistance. Actual measured values may vary due to manufacturing tolerances, material properties, and other factors. For high-precision or high-frequency applications, additional factors must be considered including skin effect, proximity effect, and dielectric losses.

Primary Formula:
Resistance \( R = \dfrac{\rho \times L}{A} \)
- \( R \): Resistance (Ohms)
- \( \rho \): Copper resistivity (Ω·m)
- \( L \): Trace length (m)
- \( A \): Cross-sectional area (m²)

What Is the PCB Trace Resistance Calculator?

The PCB Trace Resistance Calculator helps you estimate the electrical resistance, voltage drop, and power dissipation of copper traces on a printed circuit board (PCB). It factors in physical dimensions, copper thickness, temperature, and current to provide an accurate assessment of how well a trace can carry electrical current without excessive loss or heat buildup.

Whether you're designing a high-current power supply or working on precise signal routing, this tool can improve reliability and performance by helping you make informed decisions early in your design process. It's an excellent reference even if you're using an iMac computing tool or planning on circuit modeling alongside Other utilities like a Bottleneck Calculator or internet speed estimator.

Key Features

  • Supports multiple units: mm, mil, oz, μm, inches, and cm
  • Adjusts for temperature and surface plating effects
  • Visualizes resistance versus trace width in a dynamic chart
  • Compares trace resistance to standard AWG wire sizes
  • Offers design recommendations based on entered values

How to Use the Calculator

Follow these steps to use the calculator effectively:

  1. Enter the trace length and select its unit (e.g., mm or inches).
  2. Input the trace width and choose the corresponding unit.
  3. Select the copper thickness using oz, mm, or μm.
  4. Set the ambient temperature to match your application environment.
  5. Enter the expected current load in amperes.
  6. Choose the plating type used on your PCB (e.g., HASL or ENIG).
  7. Optionally, adjust advanced settings like custom resistivity or temperature coefficient.
  8. Click "Calculate Resistance" to view the results.

You’ll receive immediate insights on trace resistance, voltage drop, power loss, and more—presented in a clear summary with visual aids and helpful design tips.

Who Can Benefit?

This tool is ideal for:

  • Electronics designers checking PCB current capacity
  • Engineers evaluating power dissipation in traces
  • Students learning about copper conductivity
  • Hobbyists optimizing layout for DIY projects

It’s also helpful alongside tools like the Download Speed Calculator or Power Supply Calculator when you're assessing system-level performance.

FAQ

Q: What is a typical trace resistance?
A: It depends on trace dimensions and copper weight, but values under 0.05Ω are often acceptable for power traces.



Q: Why does temperature affect resistance?
A: As temperature increases, copper’s resistivity rises, increasing the overall resistance of the trace.



Q: What unit should I use for copper thickness?
A: PCB copper is commonly specified in ounces (oz). 1 oz ≈ 35 μm thick.



Q: How accurate are the results?
A: The calculator provides theoretical estimates based on DC resistance. Actual results may vary slightly due to manufacturing tolerances.



Q: Can this tool compare my trace to a wire?
A: Yes, it matches your trace resistance to a similar American Wire Gauge (AWG) wire, offering a practical point of comparison.

Why This Calculator Is Useful

Designing PCB traces involves balancing performance, safety, and thermal considerations. This calculator simplifies that process by giving you fast, data-driven answers to questions like:

  • Will this trace handle my expected current?
  • Is the voltage drop too high for my application?
  • Do I need wider traces or heavier copper?

Whether you’re using an Apple desktop Math tool or a browser on macOS, the calculator provides reliable insights without needing additional software. It’s a convenient part of your digital toolbox—right alongside your file transfer rate calculator or bandwidth analysis tool.