PCB Trace Width Calculator
Size the minimum trace width from current and allowed temperature rise — classic IPC-2221 formula.
What it does: Calculate how wide a PCB trace must be to safely carry a given current.
When to use it: When routing power traces or high-current paths, or setting trace widths before fabrication.
Disclaimer: This result is a reference estimate. For actual production, refer to the device datasheet / local regulations as authoritative.
MEANS To carry — within a — temperature rise, this trace must be at least — wide.
No history yet. Each calculation is automatically saved to this device.
How to use the trace width calculator
Enter current, temperature rise, and copper weight.
- 01
Enter the trace current I
The current this trace must carry continuously, in A. Accepts
2or500mA. - 02
Enter the allowed temperature rise ΔT
How many degrees the trace is allowed to rise above ambient. Commonly
10(conservative) to20°C. - 03
Pick the layer and copper weight
Outer layers dissipate heat well (k=0.048), inner layers poorly (k=0.024); 1oz copper is common. Click Calculate to get the minimum trace width.
Common copper weight conversions
Copper weight is measured in ounces per square foot; 1oz ≈ 35µm.
| Copper weight (oz) | Thickness (µm) | Thickness (mil) |
|---|---|---|
| 0.5 oz | 17.5 µm | 0.689 mil |
| 1 oz | 35 µm | 1.378 mil |
| 2 oz | 70 µm | 2.756 mil |
| 3 oz | 105 µm | 4.134 mil |
Nominal thickness of 1 oz/ft² copper ≈ 1.378 mil (34.8µm).
Common questions, answered in 3 minutes
How are IPC-2221 and IPC-2152 related?
This tool uses the classic IPC-2221 curves (simple, conservative, fine for everyday use). IPC-2152 is the newer, more accurate current-capacity standard that accounts for more factors such as heat dissipation and copper-weight distribution. For production or high current, refer to IPC-2152 and your board house's capabilities as authoritative.
What temperature rise ΔT should I use?
A conservative value is 10°C; 10–20°C is typical. The larger the allowed temperature rise, the narrower the trace needed for the same current; but too high a rise hurts reliability.
Why do inner-layer traces need to be wider?
Inner layers are enclosed by the board material and dissipate heat poorly, so IPC-2221 uses a smaller k value (0.024 vs 0.048 for outer layers); thus the same current needs about 2.6× the cross-sectional area on an inner layer.
Is the result the minimum width?
Yes, it is the minimum width that meets the set temperature rise. For actual routing, leave margin and also respect impedance and minimum-line-width process requirements.
Standards and sources referenced by this tool
| Item | Value / Formula | Source |
|---|---|---|
| Current-capacity formula | I = k · ΔT^0.44 · A^0.725 | IPC-2221 (classic charts) |
| k constant | Outer 0.048 / inner 0.024 | IPC-2221 |
| Copper weight conversion | 1 oz ≈ 1.378 mil (35µm) | Industry nominal |
Based on the classic IPC-2221 formula; for precise design refer to IPC-2152 and your board house's process capabilities.