PCB Trace Width Calculator
Calculate optimal PCB trace width for your current requirements using IPC-2221 standards. Get resistance and voltage drop estimates.
Calculator
Current (I)
↓
┌────────────────────────────┐
│▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓│ ← Copper Trace
│▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓│ Width × Thickness
└────────────────────────────┘
←─── Length ───→
Cross-section:
┌─────────────┐ ↑
│▓▓▓▓▓▓▓▓▓▓▓▓▓│ Thickness (oz)
└─────────────┘ ↓
←── Width ──→How to Use This Calculator
This PCB trace width calculator uses the IPC-2221 standard to determine the minimum trace width required for your design based on current, temperature rise, and copper thickness.
- Select Layer Type — Choose between external (top/bottom) or internal layers
- Enter Current — The maximum current the trace will carry in Amps
- Set Temperature Rise — How much the trace can heat up above ambient (typically 10-20°C)
- Choose Copper Weight — Standard is 1 oz/ft² (35µm), use 2 oz for high current
- Enter Trace Length — For voltage drop and resistance calculations
- Click "Calculate" to see the required trace width and electrical characteristics
IPC-2221 Standard
The IPC-2221 is the generic standard for printed circuit board design. It provides formulas and charts for determining trace widths based on current carrying capacity.
Key Factors
- Current (I) — Higher current requires wider traces
- Temperature Rise (ΔT) — Allowing more heating means narrower traces are acceptable
- Copper Thickness — Thicker copper can carry more current in the same width
- Layer Position — Internal layers need wider traces due to reduced heat dissipation
Important Note
IPC-2221 provides conservative estimates. For critical designs, consider additional factors like ambient temperature, nearby heat sources, and airflow. Always add a safety margin to your calculations.
PCB Trace Design Tips
Copper Weight Selection
| Copper Weight | Thickness | Typical Use |
|---|---|---|
| 0.5 oz/ft² | 17.5 µm | Fine-pitch components, RF circuits |
| 1 oz/ft² | 35 µm | Standard PCBs, most applications |
| 2 oz/ft² | 70 µm | Power electronics, high current |
| 3-4 oz/ft² | 105-140 µm | Heavy power, automotive |
Temperature Rise Guidelines
- 10°C — Conservative, good for enclosed designs or high ambient temps
- 20°C — Standard for most applications with adequate ventilation
- 30°C — Acceptable for well-cooled designs with good airflow
- 40°C+ — Only for short traces with active cooling
High Current Design Strategies
- Polygon Pours — Use copper fills instead of traces for power
- Parallel Traces — Multiple traces in parallel share current
- Thicker Copper — 2 oz copper can carry 40% more current
- Thermal Vias — Help dissipate heat to other layers
Practical Examples
Example 1: USB Power Trace (5V, 500mA)
Designing a USB device with 500mA power delivery.
Parameters: I = 0.5A, ΔT = 10°C, 1 oz copper, External
Result: Trace width ≈ 0.25mm (10 mils)
Recommendation: Use 0.3mm (12 mils) minimum for safety margin
Example 2: Motor Driver (12V, 3A)
Power traces for a DC motor driver circuit.
Parameters: I = 3A, ΔT = 20°C, 1 oz copper, External
Result: Trace width ≈ 1.0mm (40 mils)
Recommendation: Consider 2 oz copper to reduce width to 0.7mm
Example 3: LED Driver (24V, 5A)
High-current traces for an LED lighting driver.
Parameters: I = 5A, ΔT = 20°C, 2 oz copper, External
Result: Trace width ≈ 1.2mm (47 mils)
Recommendation: Use polygon pour for main power rails
Frequently Asked Questions
Why are internal traces wider than external?
Internal layers are sandwiched between other PCB layers, limiting their ability to dissipate heat through convection and radiation. External layers can cool more effectively through air contact, so they can be narrower for the same current.
What temperature rise should I use?
A 10°C rise is conservative and good for most applications. Use 20°C for well-ventilated designs. Higher values (30-40°C) are only appropriate for short traces with good thermal management. Consider your maximum ambient temperature plus the rise should not exceed component ratings.
Can I use thinner traces for signal lines?
Yes. Signal traces carrying milliamps can be much thinner than power traces. The main constraints for signals are manufacturing capability (typically 4-6 mil minimum) and impedance requirements for high-speed signals, not current capacity.
How do vias affect current capacity?
A single via has limited current capacity (typically 0.5-1A depending on size). For high current paths, use multiple vias in parallel. A common rule is one via per amp of current, but check via sizing calculations for your specific design.
Should I derate for long traces?
Long traces accumulate more resistance and voltage drop, but the IPC formula already accounts for thermal aspects. Check the voltage drop calculation to ensure it is acceptable for your circuit. For sensitive analog circuits, wider traces reduce noise from IR drop.
What about AC and high-frequency currents?
The IPC-2221 formulas are primarily for DC and low-frequency AC. At high frequencies, skin effect concentrates current at the trace surface, effectively reducing the conducting area. For RF and high-speed digital, use impedance-controlled trace calculations instead.
Verify Your Component Selections
After calculating your component values, use Schemalyzer to verify your schematic design. Our AI-powered analysis catches common errors and suggests improvements.
Try Free Schematic Review