IPC-2221 Trace Sizing

PCB Trace Width Calculator

A PHP clone of the DigiKey calculator for estimating trace width, resistance, voltage drop, and power loss for internal and external copper layers.

Use this for first-pass routing decisions.

Internal layers require wider traces for the same current and temperature rise.

Inputs

Formula

Area = (I / (k x dTb))1 / c

Width = Area / Thickness

Internal layer constants: k = 0.024, b = 0.44, c = 0.725

External layer constants: k = 0.048, b = 0.44, c = 0.725

Internal Layers

Conservative
Required Trace Width 140.0051 mil
Resistance 0.0075 ohm
Voltage Drop 0.0224 V
Power Loss 0.0671 W

External Layers in Air

Lower width
Required Trace Width 53.8183 mil
Resistance 0.0194 ohm
Voltage Drop 0.0582 V
Power Loss 0.1745 W

Assumptions

  • Width sizing follows the IPC-2221 current-temperature-rise curve fit.
  • Resistance uses copper resistivity at the estimated operating temperature.
  • The operating temperature is treated as ambient plus allowed temperature rise.
  • Results are estimates and should be verified against board stackup and fabrication limits.