PCB Trace Width Calculator
Estimate external copper trace width with a simplified IPC-2221-era equation.
PCB Design Parameters
How It Works
When designing printed circuit boards, traces must be wide enough to carry the required electrical current without overheating and damaging the board. This calculator estimates the required trace width based on the IPC-2221 formula for external PCB layers.
The calculation considers the continuous current load, copper thickness and acceptable temperature rise above ambient conditions.
PCB Design Applications
Security Hardware Design
Calculate trace widths when designing or modifying custom relay boards for access control systems, as an initial design estimate to be validated.
Power Supply Routing
Compare initial width estimates for DC copper paths. Check voltage drop and temperature in the complete board design separately.
Field Electronics Repair
Compare copper cross-sections during preliminary analysis; this estimate does not qualify or certify a board repair.
Model and worked example
The implemented equation is I = 0.048 × ΔT^0.44 × A^0.725, where I is amperes, ΔT is temperature rise in °C and A is copper cross-section in square mils. The tool solves for A, divides by copper thickness (1.378 mils per oz/ft²), then multiplies the resulting width in mils by 0.0254 to display millimeters.
At 1 A, 1 oz/ft² copper and a 10°C rise, the result is approximately 0.300 mm. This is the output of the simplified model, not a certified minimum width. Doubling copper thickness halves the model width at the same current and rise; real board thermal behavior also depends on its construction.
Temperature rise is not ambient temperature
A 10°C rise above a 40°C local ambient corresponds to a modeled conductor temperature of 50°C. It is not a universal damage threshold. Select an allowable temperature using the board materials, component ratings and operating conditions.
Where this model stops
The calculator addresses external traces and has no inputs for trace length, internal layers, copper planes, vias, enclosure conditions or transient current. It therefore does not calculate voltage drop or certify current capacity. Review the finished copper thickness with your fabricator and validate the board under representative load.
IPC-2152 provides guidance on conductor sizing and temperature relationships. This tool does not implement the full IPC-2152 method.