PCB Trace Width Calculator

Fast, embeddable widget based on IPC‑2221 (with safety factor). Compute required width for given current, temperature rise, copper weight, and layer type.

Current (A)

Allowed temperature rise (°C)

Layer type

Copper weight(s)

1 oz ≈ 35 µm ≈ 1.378 mil 2 oz ≈ 70 µm 0.5 oz ≈ 18 µm

Safety factor (× width)

Use 1.0 for raw IPC‑2221. ≥1.2 helps align with IPC‑2152 tendencies.

Formula: I = k·(ΔT)^0.44·A^0.725 ⇒ A = (I / (k·ΔT^0.44))^(1/0.725); A in mil², t in mil ⇒ w = A/t.

Results

Copper	Thickness (µm)	Required width (mm)	Required width (mil)	Cross‑section (mm²)

Notes, assumptions & limits

k constants per IPC‑2221: external k = 0.048, internal k = 0.024.
Outputs are conservative if you increase the safety factor to reflect IPC‑2152 data trends (routing, proximity, vias, convection, etc.).
Ambient temperature, airflow, adjacent copper, and board stack‑up materially affect ampacity; always validate with your fabricator and do a sanity check in context.
Rounding: widths shown to 2 decimal mm (≈0.8 mil); adjust in code for finer precision if needed.