Engineering Tools
PCB Trace Width Calculator
Calculate minimum trace width for current-carrying requirements per IPC-2152.
Calculate the minimum PCB trace width required to carry a specified current with an acceptable temperature rise. This calculator uses the IPC-2152 standard for current-carrying capacity of printed circuit board traces, which replaced the older IPC-2221 charts with more accurate thermal modeling based on extensive testing data.
How to use
Enter the current (amps), copper thickness (oz), maximum allowable temperature rise above ambient (°C), and trace location (external layer or internal layer). The calculator returns the minimum trace width in mils and mm. Internal traces run hotter than external traces for the same current because they have less ability to dissipate heat — the surrounding dielectric insulates them from convective and radiative cooling.
Understanding the results
The calculated trace width represents the minimum dimension that keeps the temperature rise at or below your specified limit. In practice, use a trace width at least 10-20% wider than the calculated minimum to provide margin for manufacturing tolerance (etching reduces trace width from the design value), worst-case operating conditions, and thermal interaction with adjacent traces and components that the simplified model does not capture.
Temperature rise is relative to ambient — if the board operates inside an enclosure at 60°C ambient and the copper has a maximum rated temperature of 105°C, the allowable temperature rise is 45°C, not the default 10°C that many designers use. Setting the correct temperature rise is essential for getting a useful result from the calculator.
Copper weight and current capacity
Heavier copper carries more current at the same trace width, or the same current at a narrower trace width. A 10-mil trace in 1 oz copper carries approximately 1.0 amp with 10°C rise. The same trace in 2 oz copper carries approximately 1.7 amps. For high-current applications (power supplies, motor drives, battery chargers), 2-4 oz copper on the power layers significantly reduces the trace width required and the associated resistive heating.
Limitations
This calculator models a single isolated trace in still air. Real boards have multiple traces in close proximity, components generating heat, varying airflow conditions and copper planes that affect thermal spreading. For critical power paths where thermal performance affects product reliability, thermal simulation of the actual layout provides more accurate results than any single-trace calculator.
For production boards, AstroPCB’s engineering team can review your power distribution layout and verify that trace widths and copper weights are adequate for the specified current with acceptable temperature rise.