PCB Trace Width Calculator
Calculate the optimal PCB trace width needed to safely carry a specified current while maintaining thermal limits.
Calculate Your PCB Trace Width Calculator
Determining PCB Trace Width for Current Requirements
Selecting the appropriate trace width is critical in PCB design to ensure that traces can safely carry the required current without overheating or causing voltage drops that affect circuit performance. The width calculation considers several factors including current, allowed temperature rise, copper thickness, and trace location.
The IPC-2152 Standard
The industry standard for determining trace width is IPC-2152, "Standard for Determining Current-carrying Capacity in Printed Board Design." This standard provides charts and equations based on extensive thermal testing for calculating the appropriate trace width for a given current.
IPC-2152 replaced the older IPC-2221 standard and offers more accurate recommendations across different scenarios, accounting for:
- Current requirements
- Allowable temperature rise
- Copper weight (thickness)
- Trace location (internal vs. external)
- Trace length
- Board thermal properties
Key Factors in Trace Width Calculation
Current
The primary factor determining trace width is the maximum current the trace must carry. Higher currents require wider traces to prevent excessive heating. Remember to account for both continuous and peak current requirements.
Temperature Rise
The allowable temperature increase above ambient temperature affects the required trace width. Lower allowed temperature rises (safer design) require wider traces. Most designs use 10-20°C temperature rise as a general guideline, but critical applications may require more conservative values.
Copper Thickness
PCB copper thickness is specified in ounces per square foot (oz/ft²), commonly available in 0.5 oz, 1 oz, 2 oz, and 3 oz options. Thicker copper allows narrower traces for the same current capacity. For example, a 2 oz trace can carry approximately 40% more current than the same width 1 oz trace.
Trace Location
Traces on external layers can dissipate heat more effectively than internal traces. As a result, internal traces typically need to be 1.5-2 times wider than external traces to carry the same current.
Practical Guidelines
While the calculator provides specific recommendations based on your inputs, here are some general guidelines for quick reference (assuming 1 oz copper on external layer and 10°C temperature rise):
| Current | Approx. Trace Width (External) | Approx. Trace Width (Internal) |
|---|---|---|
| 0.5 A | 8 mil (0.2 mm) | 12 mil (0.3 mm) |
| 1 A | 15 mil (0.38 mm) | 25 mil (0.64 mm) |
| 2 A | 30 mil (0.76 mm) | 50 mil (1.27 mm) |
| 3 A | 45 mil (1.14 mm) | 75 mil (1.9 mm) |
| 5 A | 80 mil (2.0 mm) | 125 mil (3.2 mm) |
| 10 A | 180 mil (4.6 mm) | 300 mil (7.6 mm) |
Design Considerations
- Safety Margin: It's good practice to add a safety margin to your current requirements when calculating trace width, especially for critical circuits.
- Space Constraints: When space is limited but current requirements are high, consider using heavier copper, multiple parallel traces, or multiple layers connected with vias.
- High-Current Solutions: For currents above 5-10A, consider using copper pours, bus bars, or specialized power planes instead of discrete traces.
- Thermal Consideration: Remember that adjacent traces carrying high current can heat each other, potentially requiring wider traces than calculated for isolated traces.
- Via Current: When high-current traces must change layers, use multiple vias in parallel, as vias have significantly less current capacity than traces.
This calculator provides a good starting point for trace width determination, but final designs should always be verified against applicable standards and tested where appropriate, especially for critical applications or high-current designs.
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