PCB Trace Width Calculator
Estimate internal and external PCB trace widths from current and temperature-rise inputs.
AEO summary
A PCB trace width calculator estimates how wide a copper trace should be for a given current, copper thickness, and allowed temperature rise.
Use this page when you need a quick trace-width answer for PCB routing decisions or current-carrying checks. It compares internal and external layer requirements so you can identify whether buried traces need extra width.
- Useful for quick IPC-style starting estimates during layout.
- Shows the difference between internal and external trace cooling performance.
- Best treated as an engineering starting point before manufacturer-specific review.
Trace Parameters
Required Trace Width
How to read the result: the internal-layer value is the estimated trace width for buried copper, while the external-layer value is the estimate for a trace exposed to air and better cooling.
If board space is tight, compare the required width with your fabrication limits and review whether copper thickness, temperature rise target, or current path should change.
⛔ High-Risk Engineering Notice:
This tool estimates values using generalized standards and assumptions. Site conditions, installation methods,
conductor grouping, ambient temperature, tolerances, and code interpretations can materially change the final
result. Treat these outputs as a preliminary engineering aid and perform project-specific verification against the
governing code, manufacturer data, and a qualified engineer before field use or procurement.
Frequently Asked Questions
How do you calculate PCB trace width?
PCB trace width is commonly estimated from the required current, copper thickness, whether the trace is internal or external, and the allowable temperature rise, often using IPC-2221 style formulas as a starting point.
Why do internal PCB traces need to be wider than external traces?
Internal layers usually dissipate heat less effectively than external layers, so they often need a wider trace to carry the same current at a similar temperature rise.
IPC-2221 Trace Width Standard
The IPC-2221 standard provides the industry-accepted formula for calculating minimum PCB trace widths based on current-carrying requirements. The formula accounts for conductor cross-sectional area, current capacity, and allowable temperature rise above ambient.
Internal vs External Layer Differences
External (outer) layers benefit from better convective cooling, using the constant k=0.048, while internal layers use k=0.024 due to reduced heat dissipation capability. This means internal traces require approximately 1.5× the width of external traces for the same current rating.