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Trace Width Calculator
Calculate minimum PCB trace width for current carrying capacity using IPC-2221.
A
°C
Minimum Trace Width
Cross Section
16.30 mil²
Resistance
4165.072 mΩ/inch
Note: This calculator uses IPC-2221 standards. Results are minimum values - always add safety margin and verify with your PCB manufacturer's capabilities.
Common Trace Widths (1oz, 10°C Rise)
| Current | External | Internal |
|---|---|---|
| 0.5 A | 6 mil | 12 mil |
| 1.0 A | 10 mil | 20 mil |
| 2.0 A | 20 mil | 39 mil |
| 3.0 A | 30 mil | 58 mil |
| 5.0 A | 48 mil | 95 mil |
How It Works
This calculator uses the IPC-2221 standard formula to determine minimum trace width based on:
- Current (I): The maximum current the trace needs to carry
- Temperature Rise (ΔT): Acceptable temperature increase above ambient
- Copper Weight: Thickness of copper layer (1 oz = 35 μm = 1.378 mil)
- Layer Type: External traces cool better than internal traces
I = k × ΔT0.44 × A0.725
where k = 0.048 (external) or 0.024 (internal), A = cross-sectional area in mil²
Design Guidelines
Temperature Rise Selection
- 10°C: Conservative, good for most applications
- 20°C: Common for general digital circuits
- 30°C: Maximum recommended for reliability
- 45°C: Aggressive, use with caution
Safety Margins
- Add 20-50% to calculated width for safety
- Consider voltage drop for long traces
- Account for manufacturing tolerances
- Use wider traces near heat sources
Frequently Asked Questions
What temperature rise should I use?
For most applications, 10°C is a safe choice. Higher values (20-30°C) can be used where board temperature is less critical, but stay under 45°C for reliability.
Why are internal traces wider?
Internal traces are surrounded by FR4 dielectric which is a poor thermal conductor. External traces can dissipate heat to air more efficiently, allowing them to be narrower for the same current.
Does this account for voltage drop?
This calculator focuses on thermal limits. For power distribution, also verify voltage drop is acceptable using our Voltage Drop Calculator.