PCB Trace & Via Calculator (IPC-2221)

IPC-2221: I = k × ΔT^0.44 × A^0.725, where A = thickness × width (mil²)

k values: 0.048 (external), 0.024 (internal)

Trace Resistance: R = ρ × L / (width × thickness), ρ(Cu) = 1.68×10⁻⁸ Ω·m

Via Resistance: R ≈ ρ × L / (π × D_avg × t_plating)

IPC-2221 formula is conservative. IPC-2152 may allow narrower traces for the same current.