About the PCB Trace Width Calculator
What is the PCB Trace Width Calculator?
Copper traces heat up when carrying current. This PCB trace width calculator uses the IPC-2221 formula to find the narrowest trace that keeps the temperature rise within your limit.
External layers cool better than internal ones, so they can carry about twice the current for the same width.
How to use the PCB Trace Width Calculator
- Current (A) (sample: 3)
- Allowed Temperature Rise (°C) (sample: 10)
- Copper Weight (oz/ft²) (sample: 1)
- Layer (sample: External (outer) layer)
- Trace Length (mm) (sample: 50)
- Press Calculate Trace Width (results also refresh as you type). The result card shows the Minimum Trace Width, along with Width in mils, Copper cross-section, Copper thickness and Trace resistance.
Formula used
I = k × ΔT^0.44 × A^0.725
- k = 0.048 for external layers, 0.024 for internal layers
- A = cross-section in square mils; width = A ÷ (1.378 × copper oz)
IPC-2152 gives more refined charts, but IPC-2221 remains the common quick-design rule.
Worked example
These are the sample values already filled in the calculator above, and the result it returns for them:
| Input | Sample value |
|---|---|
| Current (A) | 3 |
| Allowed Temperature Rise (°C) | 10 |
| Copper Weight (oz/ft²) | 1 |
| Layer | External (outer) layer |
| Trace Length (mm) | 50 |
| Result | Value |
|---|---|
| Minimum Trace Width | 1.367 mm |
| Width in mils | 53.8 mil |
| Copper cross-section | 74.2 mil² |
| Copper thickness | 35 µm |
| Trace resistance | 19.03 mΩ |
| Voltage drop | 57.1 mV |
| Power loss | 171.3 mW |
Tips for using the PCB Trace Width Calculator
- 1 oz copper is about 35 µm thick; 2 oz doubles the current capacity for the same width.
- Widen power traces beyond the minimum to reduce voltage drop.