Inner-Layer Trace Width Calculator
Why internal traces need double the copper — IPC-2221 internal-k presets, 0.5 oz inner foil reality and via-stitch budgets.
Preset for this niche — adjust to your stack-up. IPC-2221 assumes still air; verify hot paths with a thermal camera.
Inner Layer Trace Width Calculator computes trace sizing on internal layers where IPC-2221's half-constant applies — free, instant and private in your browser. Multilayer designers jogging power nets through inner layers use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About Inner-Layer Trace Width Calculator
Inner Layer Trace Width Calculator computes trace sizing on internal layers where IPC-2221's half-constant applies using the standard engineering relation: IPC-2221 internal presets: k = 0.024, typically 0.5 oz inner foil — roughly double the area of outer layers. Worked live: a current that needs 0.3 mm outside demands ~1.2 mm on a 0.5 oz inner layer. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use Inner-Layer Trace Width Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use Inner-Layer Trace Width Calculator?
- ✓Implements the real formula — IPC-2221 internal presets: k = 0.024, typically 0.5 oz inner foil — roughly double the area of outer layers — with the substitution shown, not a black box
- ✓Built for multilayer designers jogging power nets through inner layers
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate inner layer trace width?+
Trace sizing on internal layers where IPC-2221's half-constant applies follows IPC-2221 internal presets: k = 0.024, typically 0.5 oz inner foil — roughly double the area of outer layers. For example, a current that needs 0.3 mm outside demands ~1.2 mm on a 0.5 oz inner layer. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
Is my 4-layer board's '1 oz copper' really 1 oz everywhere?+
Usually not — standard stackups put 1 oz outside and 0.5 oz on inners unless you pay for more. Check the fab's stackup table: assuming outer-layer math on a 0.5 oz inner trace under-sizes it 4× (half the constant × half the copper).
How many vias when power dives to an inner layer and back?+
Budget ~1 A per standard 0.3 mm via at 10 °C rise, then round up: a 3 A jog wants 3–4 vias clustered at EACH transition. The vias often constrain the design more than the inner trace itself — which is the quiet argument for keeping power on outer layers.
Is the Inner Layer Trace Width Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
Related Electronics tools
PCB Trace Width Calculator (IPC-2221)
Minimum trace width for your current and temperature rise — IPC-2221 formula with copper weight, layer choice and a step-by-step worked example.
● LiveMicrostrip Impedance Calculator
Z₀ of a surface microstrip from width, height and εr (IPC-2141A), plus effective dielectric constant and propagation delay.
● LiveStripline Impedance Calculator
Characteristic impedance of an embedded stripline trace from geometry and εr — the inner-layer companion to the microstrip tool.
● Live