PCB Trace Width Calculator – Calculate Copper Trace Width
Calculate minimum PCB trace width for a given current using IPC-2221 guidelines. Prevents overheating and ensures reliability.
Enter the current
Input the maximum current in Amperes that will flow through the trace.
Select copper weight and layer type
Choose the copper thickness (oz/ft²) and whether the trace is on an external or internal layer.
Set temperature rise and calculate
Enter the maximum acceptable temperature rise above ambient. Click Calculate to see the minimum trace width.
| Copper Weight | Thickness (mm) | Thickness (mils) | Typical Use |
|---|---|---|---|
| 0.5 oz/ft² | 0.0175 | 0.7 | Low-power signal traces |
| 1 oz/ft² | 0.035 | 1.4 | Standard PCBs |
| 2 oz/ft² | 0.070 | 2.8 | High current, power supplies |
| 3 oz/ft² | 0.105 | 4.2 | Heavy current applications |
Why Trace Width Matters
PCB traces have resistance. When current flows, they heat up. Too narrow a trace means too much resistance, leading to excessive heat that can damage the board or cause failure. The IPC-2221 standard provides guidelines for minimum trace widths based on current, copper thickness, and acceptable temperature rise.
External vs Internal Layers
External layers dissipate heat better because they're exposed to air. Internal layers are sandwiched between substrate material, trapping heat. For the same current, internal traces need to be wider than external traces. This calculator accounts for that difference.
Temperature Rise Guidelines
A 10°C temperature rise is conservative and suitable for most applications. 20°C is common for commercial products. Higher rises may be acceptable in well-ventilated or short-duration applications. Consider your operating environment and reliability requirements.
Use Wider When Possible
The calculated width is a minimum. Wider traces reduce resistance and improve reliability at no extra cost.
Consider Voltage Drop
Long traces have resistance that causes voltage drop. Check that the drop is acceptable for your application.
Use Multiple Layers
For very high currents, use traces on multiple layers connected with vias to share the load.
Add Solder Mask Openings
For high-current traces, expose copper and add solder to increase current capacity.
What is the IPC-2221 standard?
IPC-2221 is a generic standard for printed board design. It includes formulas for calculating trace width based on current, copper thickness, and temperature rise. The formulas in this calculator are derived from IPC-2221 guidelines.
How do I convert between oz and mm for copper?
1 oz/ft² copper equals 0.035 mm (1.4 mils) thickness. This refers to the weight of copper per square foot, which correlates to thickness. Common values: 0.5 oz = 0.0175mm, 1 oz = 0.035mm, 2 oz = 0.070mm.
What temperature rise should I use?
10°C is conservative and works for most applications. 20°C is common for consumer electronics. Higher rises reduce trace width but increase heat. Consider your enclosure, airflow, and reliability requirements.
Why are internal traces wider than external?
Internal layers are surrounded by substrate material that insulates and traps heat. External layers can dissipate heat to air. For the same current and temperature rise, internal traces need about 2x the cross-sectional area.
Can I use this for high-frequency signals?
This calculator is for DC and low-frequency current capacity. High-frequency signals need impedance-controlled traces, which depend on trace geometry and dielectric properties. Use an impedance calculator for RF designs.
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