PCB Trace Width Calculator
Size a PCB copper trace by current, target current density and copper thickness. Reports width in mm and mils plus the cross-section.
How to Use the PCB Trace Width Calculator
- Enter the expected trace current in amperes.
- Pick a current density (A/mm²) suited to your layer and ambient.
- Enter the copper thickness in µm (35 µm = 1 oz).
- Click Calculate.
Cas d'utilisation
- •Power plane and rail design.
- •Motor driver PCBs.
- •Battery management system layouts.
Formule
Simplified IPC-2221 style: w = I / J (mm), where J is the allowable current density in A/mm². Convert to mils: w_mil = w_mm / 0.0254.
Questions fréquemment posées
Which standard?
IPC-2221 (1998) is the de facto reference for PCB trace sizing. Its external-layer curves correspond to about 4–6 A/mm² for a 10 °C rise; internal layers derate by roughly half.
How do I pick current density?
Use 4 A/mm² for external traces with modest temperature rise, 2 A/mm² for inner layers, and lower for long runs or fine pitch. High-power designs often use 1–2 A/mm².
Does copper thickness matter?
Yes. Standard 1 oz/ft² copper equals 35 µm; 2 oz equals 70 µm. Thicker copper allows narrower traces at the same current.