How to Use PCB Trace Current Calculator
- Select whether the trace is on an outer layer or inner layer. Outer layers generally dissipate heat better in the IPC-2221 model.
- Enter trace width, copper thickness, allowed temperature rise, and trace length. Use mil/mm and oz/µm selectors to match your source data.
- Use current mode to estimate how much current the entered trace may carry.
- Review resistance, voltage drop, and power loss when trace length and current are relevant to the design.
Formula & Theory - PCB Trace Current Calculator
I = k × ΔT^0.44 × A^0.725
A = W × T
Outer layer k = 0.048
Inner layer k = 0.024IPC-2221 uses an empirical relationship between cross-sectional area, temperature rise, and current. The formula is useful for early sizing because it needs only a few inputs.
The cross-sectional area is width multiplied by copper thickness. The same current causes more heating in smaller copper area, and inner traces use a lower k factor.
The result is conservative for some modern boards and optimistic for others. Copper pours, vias, airflow, board thickness, ambient temperature, adjacent heat sources, and IPC-2152 data can all change the answer.
Use Cases for PCB Trace Current Calculator
- Sizing a trace before a PCB layout review.
- Comparing outer-layer and inner-layer routing for a power path.
- Estimating voltage drop in a long low-voltage trace.
- Documenting why a wider trace or copper pour is needed for high current.