PCB Track Width Calculator (IPC-2221)
Calculate the minimum PCB track width for your current requirements using the IPC-2221 standard. Get instant results with resistance, voltage drop, and power dissipation calculations.
⚙️ Parameters
Expected current through the trace
Standard is 1 oz (35 µm / 1.37 mils)
Typical: 5-10°C for normal operation
Internal layers require wider traces (worse cooling)
For resistance and voltage drop calculation
📊 Results
Minimum Width (IPC-2221)
---
--- mils
Recommended Width (20% margin)
---
Resistance
---
Voltage Drop
---
Power Dissipation
---
Cross-sectional Area
---
📐 Visual Reference
Save Your Calculation
Export results for use in KiCad or documentation
Theory & Formulas
IPC-2221 Formula
The IPC-2221 standard provides the industry-standard formula for calculating current-carrying capacity of PCB traces:
I = Current in Amperes
K = 0.048 for external layers, 0.024 for internal layers
ΔT = Temperature rise above ambient in °C
A = Cross-sectional area in square mils (1 mil = 0.001 inch)
Width Calculation
The trace width is calculated from the cross-sectional area:
Standard copper weights: 0.5 oz = 17.5µm, 1 oz = 35µm, 2 oz = 70µm, 4 oz = 140µm
Resistance & Power
Resistance and power dissipation calculations use copper's resistivity (ρ = 1.68×10⁻⁸ Ω·m at 20°C):
R = ρ × L / A
Vdrop = I × R
P = I² × R
💡 Design Tip: Always add a safety margin (typically 20-30%) to calculated values. Consider worst-case ambient temperature and account for thermal management.
Frequently Asked Questions
What's the difference between external and internal layers?
External layers (top and bottom) have better thermal cooling through air convection. Internal layers are sandwiched between dielectric material with poorer heat dissipation, requiring wider traces for the same current (K factor is halved).
Should I use the minimum or recommended width?
Always use the recommended width (with 20% safety margin) or wider. The minimum width is theoretical and doesn't account for manufacturing tolerances, aging effects, or thermal variations. For critical power traces, consider 30-50% margin.
How do I use this with KiCad?
Use "Export KiCad Rules" to generate design rule constraints. Copy the output and paste into your KiCad design rules editor (Board Setup → Design Rules → Constraints). Our KiCad plugin (coming soon) will provide direct integration.
What temperature rise should I use?
10°C is a safe default for general electronics. Use 5°C for precision analog circuits or harsh environments. For non-critical digital signals, 15-20°C may be acceptable. Never exceed 30°C rise unless you have specific thermal analysis.