Trace Width Calculator

Current (Amps):

Temperature Rise (°C):

Copper Weight:

Layer Type:

Trace Length (inches):

Designing printed circuit boards (PCBs) requires careful attention to the size of copper traces, especially when they carry significant electrical current. The trace width directly affects how much current a trace can safely handle without overheating or causing excessive voltage drops. Improperly sized traces can lead to device failure, reliability issues, or inefficient designs.

The Trace Width Calculator is a powerful yet simple tool that helps PCB designers, engineers, and hobbyists quickly determine the minimum trace width needed based on your current load, temperature rise tolerance, copper thickness, trace length, and layer type. Additionally, it calculates important parameters like trace resistance, voltage drop, and power dissipation, giving you a comprehensive understanding of the trace’s electrical behavior.

What is the Trace Width Calculator?

The Trace Width Calculator is an interactive online tool designed to compute:

Minimum trace width in mils (thousandths of an inch) and millimeters
Cross-sectional area of the trace in mil²
Trace resistance in milliohms (mΩ)
Voltage drop across the trace in millivolts (mV)
Power dissipation in milliwatts (mW)

It factors in important PCB design parameters such as copper weight (thickness), layer location (internal or external), allowable temperature rise, and trace length to ensure your trace sizing meets both thermal and electrical requirements.

How to Use the Trace Width Calculator

1. Input Current (Amps)

Enter the maximum continuous current your trace is expected to carry.

2. Enter Temperature Rise (°C)

Specify how much temperature increase above ambient temperature is acceptable for your trace. Default is often 10°C but adjust based on your design limits.

3. Select Copper Weight

Choose from common copper thicknesses:

0.5 oz (17.5 µm)
1 oz (35 µm)
2 oz (70 µm)
3 oz (105 µm)
4 oz (140 µm)

Higher copper weights allow narrower traces for the same current.

4. Choose Layer Type

Select External Layer for outer PCB layers or Internal Layer for inner layers. Internal layers dissipate heat less efficiently, requiring wider traces.

5. Enter Trace Length (inches)

Provide the length of the trace for calculating resistance, voltage drop, and power dissipation.

6. Calculate Results

Click Calculate to display:

Minimum trace width (mils and mm)
Cross-sectional area (mil²)
Trace resistance (mΩ)
Voltage drop (mV)
Power dissipation (mW)

7. Reset Inputs

Use the Reset button to clear all fields and start fresh.

Example: Designing a Trace for 3 Amps with 1 oz Copper

Suppose you have a PCB trace that will carry 3 Amps current with a maximum temperature rise of 10°C. You are using 1 oz copper thickness on an external layer, and the trace length is 2 inches.

Input:

Current: 3 A
Temperature Rise: 10°C
Copper Weight: 1 oz
Layer Type: External
Trace Length: 2 inches

Result Highlights:

Minimum Trace Width: About 23 mils (~0.58 mm)
Cross-Sectional Area: Calculated value based on width and thickness
Trace Resistance: Computed for 2-inch trace length
Voltage Drop and Power Dissipation: Reflect real operating conditions

This helps you define a trace width that prevents overheating and ensures proper circuit function.

Why Is Proper Trace Width Critical?

Thermal Safety: Prevents traces from overheating and damaging PCB or components.
Electrical Integrity: Minimizes voltage drop and signal loss for stable operation.
Reliability: Proper sizing reduces the risk of trace failure and improves product lifespan.
Space Optimization: Avoids oversized traces that waste PCB real estate and increase costs.
Regulatory Compliance: Ensures designs meet IPC-2152 and other industry standards.

Important Factors in Trace Width Calculation

Current: More current demands wider traces.
Temperature Rise: Higher allowable temperature means smaller traces but increased risk.
Copper Weight (Thickness): Thicker copper layers allow narrower traces.
Layer Type: Internal layers require wider traces due to limited heat dissipation.
Trace Length: Affects resistance, voltage drop, and power dissipation, though not trace width directly.

Frequently Asked Questions (FAQs)

1. How accurate is this calculator?
It follows IPC-2152 standard approximations, widely accepted in PCB design.

2. Can I use it for both internal and external layers?
Yes, it differentiates between layer types affecting heat dissipation.

3. What units are used for trace width?
Mils (thousandths of an inch) and millimeters.

4. Why does copper weight affect trace width?
Thicker copper conducts better, requiring less width for the same current.

5. Is temperature rise optional?
No, you must specify it to define the thermal limits of your design.

6. How do I choose temperature rise?
Consider your device’s operating environment and reliability needs.

7. Does trace length impact trace width?
Not directly, but it affects resistance, voltage drop, and power loss calculations.

8. Can this tool calculate power dissipation?
Yes, it shows estimated power lost due to trace resistance.

9. How can I reduce voltage drop on my trace?
Increase trace width, reduce length, or use thicker copper.

10. What happens if the trace is too narrow?
Overheating, voltage drop, and possible trace burnout.

11. Are the results suitable for high-frequency signals?
Primarily for DC or low-frequency current carrying capacity, not impedance control.

12. Can I use this for flexible PCBs?
Yes, but consider additional mechanical constraints not included here.

13. How often should I update copper thickness values?
When changing PCB specs or manufacturer capabilities.

14. Is the cross-sectional area output useful?
Yes, it helps understand the physical size of the trace cross-section.

15. What is a safe margin for temperature rise?
Typically 10°C, but sensitive designs may use lower values.

Conclusion

The Trace Width Calculator is an essential tool that streamlines PCB design by ensuring your traces can safely carry current while maintaining electrical and thermal integrity. With clear inputs and comprehensive outputs, it enables you to optimize your PCB layouts for performance, reliability, and cost-efficiency.

Leverage this calculator for every PCB project to build robust and efficient circuits with confidence. Accurate trace sizing is just a few clicks away!