PCB Trace Width Calculator – Free Online PCB trace width calculator

Calculate the minimum PCB trace width for a given current using IPC-2221, for external and internal layers.

Layer	Width (mil)	Width (mm)	Resistance	Voltage drop	Power loss
External	30.8	0.781	32.68 mΩ	65.36 mV	130.72 mW
Internal	80	2.033	12.562 mΩ	25.12 mV	50.25 mW

IPC-2221: I = k × ΔT^0.44 × A^0.725, k = 0.048 (external) or 0.024 (internal), A in mil². Copper thickness 1.378 mil per oz. Valid up to about 35 A, 400 mil width and 10–100 °C rise; IPC-2152 gives less conservative internal widths.

About this PCB trace width calculator

Find the minimum copper trace width for a given current with the IPC-2221 formula. Results are shown for external and internal layers, together with the trace resistance, voltage drop and power loss for the entered length.

How to use the PCB Trace Width Calculator

Enter the current and allowed temperature rise.
Choose the copper weight and trace length.
Read the width for external and internal layers.

Example

1 A, 10 °C rise, 1 oz external  →  ≈ 11.8 mil (0.3 mm)

Frequently asked questions

Why are internal traces wider?

Inner layers are surrounded by laminate and cannot dissipate heat to air, so IPC-2221 uses half the constant (0.024 vs 0.048).

IPC-2221 or IPC-2152?

IPC-2221 is the classic, conservative chart. IPC-2152 is newer and often allows narrower internal traces; use it for tight designs.

Is my data safe?

Yes. The tool runs entirely in your browser using WebAssembly. Nothing you type or upload is sent to a server, logged or stored.

Is it free?

Yes, completely free with no sign-up, no limits and no watermarks. It also works offline once the page has loaded.