PCB Trace Width Calculator
Calculate the required trace width for your PCB design based on current, copper weight, and acceptable temperature rise using IPC-2221 standards.
Interactive Trace Calculator
Thickness: 1.37 mils (34.8 μm)
💡 Results update in real-time as you adjust values
Live Results
Trace Width
7.81mils
Trace Width
0.20mm
⚙️ Configuration
⚠️ Safety Note: Add 10-20% margin for manufacturing tolerances and safety.
Current vs Trace Width(Your point: 0A → 0 mils)
💡 Interactive Chart: The red dot shows your current calculation. Adjust the sliders above to see how the trace width changes in real-time.
IPC-2221 Formula Details
- A: Cross-sectional area (mils²)
- I: Current (Amperes)
- ΔT: Temperature rise (°C)
- k, b, c: Constants based on layer type
Design Guidelines
- Safety Margin: It is recommended to add a 10-20% margin to calculated widths to account for manufacturing variations and potential over-current events.
- Copper Weight: Higher copper weights (e.g., 2oz vs 1oz) allow for narrower traces while handling the same amount of current.
- Layer Type: External traces can generally handle more current than internal traces due to better heat dissipation into the surrounding air.
- Manufacturing: Always consider your PCB manufacturer's capabilities, particularly their minimum trace width and spacing requirements.
IPC Standards
This calculator is based on the IPC-2221B generic standard on printed board design. This standard provides the formulas for determining the conductor width required to limit temperature rise to a specific amount.
Constants Used:
- External Layers: k = 0.048, b = 0.44, c = 0.725
- Internal Layers: k = 0.024, b = 0.44, c = 0.725
Common Trace Widths
| Current (A) | 1 oz Copper (mils) | 2 oz Copper (mils) | 20 deg C Rise |
|---|---|---|---|
| 0.5A | 3.0 | 1.5 | External |
| 1A | 7.8 | 3.9 | External |
| 2A | 20.3 | 10.2 | External |
| 3A | 35.5 | 17.8 | External |
| 5A | 71.9 | 36.0 | External |
| 10A | 187.1 | 93.5 | External |
Frequently Asked Questions
What is the IPC-2221 standard?
IPC-2221 is the generic standard for printed circuit board (PCB) design published by IPC, the global electronics manufacturing standards organization. It defines baseline design requirements and guidance that apply across a wide range of PCB technologies and serves as the foundation for more specialized, sectional standards (such as rigid, flexible, or high-speed boards). IPC-2221 includes widely used design relationships, such as the formulas that relate current-carrying capacity, copper thickness (weight), conductor width, and allowable temperature rise which are commonly implemented in PCB design calculators. Because it is technology-agnostic, it is considered the industry reference standard for general-purpose PCB design, with other IPC-222x standards building upon or refining its requirements for specific applications.
How does temperature rise affect trace width?
As current flows through a trace, it generates heat due to resistance. "Temperature Rise" defines how much hotter the trace is allowed to get above the ambient temperature. Allowing a higher temperature rise (e.g., 20°C vs 10°C) means the trace can be narrower because it's permitted to get hotter.
What is the difference between internal and external layers?
External layers are on the surface of the PCB and are exposed to air, which helps dissipate heat. Internal layers are sandwiched between other layers of substrate, insulating them and trapping heat. Therefore, internal traces typically need to be wider than external traces to carry the same amount of current for the same temperature rise.
Why use higher copper weight?
Copper weight (e.g., 1oz, 2oz) refers to the thickness of the copper layer. Thicker copper (higher weight) has a larger cross-sectional area for the same width, reducing resistance and allowing more current to flow. Using 2oz copper instead of 1oz allows you to use a trace approximately half the width for the same current capacity.