Trace Width Calculator
This Javascript web calculator calculates the trace width for printed circuit board conductors for a given current using formulas from IPC-2221 (formerly IPC-D-275).
Inputs:
| Current | Amps | |
|---|---|---|
| Thickness |
Optional Inputs:
| Temperature Rise | ||
|---|---|---|
| Ambient Temperature | ||
| Trace Length |
Results for Internal Layers:
| Required Trace Width | ||
|---|---|---|
| Resistance | Ohms | |
| Voltage Drop | Volts | |
| Power Loss | Watts |
Results for External Layers in Air:
| Required Trace Width | ||
|---|---|---|
| Resistance | Ohms | |
| Voltage Drop | Volts | |
| Power Loss | Watts |
Notes
The trace width is calculated as follows:
First, the Area is calculated:
Area[mils^2] = (Current[Amps]/(k*(Temp_Rise[deg. C])^b))^(1/c)
Then, the Width is calculated:
Width[mils] = Area[mils^2]/(Thickness[oz]*1.378[mils/oz])
For IPC-2221 internal layers: k = 0.024, b = 0.44, c = 0.725
For IPC-2221 external layers: k = 0.048, b = 0.44, c = 0.725
where k, b, and c are constants resulting from curve fitting to the IPC-2221 curves
Disclaimer
These calculations are believed to be correct, but not guaranteed. Use at your own risk!
FAQs
Very cool PCB width tool! I would like to know its limits though. I entered a 65 amp current requirement and it returned a track width that must be incorrect.
I used your PCB trace width calculator. Intuitively I would say the required internal trace width would be less than the external case since the external trace can peal off; the opposite is true according to the calculator???? Why?
What does temperature rise mean and how does it apply?
I use "wagon wheels" or "spokes" when connecting to a ground plane to make it easier to solder to. The trace width calculator is telling me to make the "spokes" so wide that it defeats the purpose. What should I do?
What are Mils?