How to Use PCB Trace Width Calculator
- Choose Find width from target current when you need a recommended minimum width.
- Enter target current, copper thickness, allowable temperature rise, and whether the trace is inner or outer layer.
- Switch to the current-estimate mode when you already have a proposed width and want to see its approximate current capacity.
- Compare the mil and mm width outputs before setting PCB design rules.
Formula & Theory - PCB Trace Width Calculator
A = (I / (k × ΔT^0.44))^(1 / 0.725)
W = A / T
Outer layer k = 0.048
Inner layer k = 0.024
1 oz copper ≈ 1.378 milThe width calculator rearranges the IPC-2221 current equation to solve for required cross-sectional area, then divides by copper thickness to get width.
Lower allowed temperature rise requires a larger trace. Inner traces also require more copper area in this model because they dissipate heat less effectively.
IPC-2221 is an early design estimate. High-current boards should also consider IPC-2152, thermal simulation, copper pours, vias, connectors, solder, airflow, and manufacturer limits.
Use Cases for PCB Trace Width Calculator
- Setting a first-pass design-rule width for power nets.
- Comparing how 1 oz versus 2 oz copper changes required routing width.
- Estimating whether an inner-layer power route is practical.
- Documenting why a target current needs a copper pour instead of a narrow trace.