PCB Trace Width Calculator

Current (A)

Temperature rise (°C)

Copper weight0.5 oz (17 µm)1 oz (35 µm)2 oz (70 µm)3 oz (105 µm)

LayerOuter (top/bottom)Inner

Trace length (mm, optional)

Ambient (°C)

About this tool

The IPC-2221 formula

I = k × ΔT^0.44 × A^0.725, where A is the copper cross-section in square mils, ΔT the temperature rise in °C, and k = 0.048 for outer layers or 0.024 for inner layers (inner traces can't shed heat to the air). Width = A ÷ copper thickness.

Choosing the temperature rise

10 °C is a common, conservative choice. 20–30 °C is fine for short power traces if nearby parts tolerate the heat. Add a margin for vias, which carry less current than the trace.

Limits

The formula comes from old IPC charts and is deliberately conservative. IPC-2152 is the newer, more detailed standard and often allows narrower traces, especially with ground planes nearby.