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Trace Width Calculator

Q: 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.

The original graphs that this tool is based on (published in IPC-2221) only cover up to 35 Amps, up to 0.4 inches of trace width, from 10 to 100 degrees C of temperature rise, and copper of 0.5 to 3 ounces per square foot. The formulas used here will simply extrapolate when the values are outside of these ranges.

Q: 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?

In air, the external layers have better heat transfer due to convection. A good heat insulator blankets the internal layers, so they get hotter for a given width and current. Since the Trace Width Calculator tries to control the temperature rise of the traces, it makes the internal traces wider. In vacuum, or in a potted assembly, you should use the internal layer guidelines even for the external layers.

Q: What does temperature rise mean and how does it apply?

Temperature rise means how much hotter the trace will get with current flowing in it compared to without. You have to decide how much temperature rise your board can handle based on the operating environment and the type of PWB material used. Ten degrees is a very safe number to use for just about any application. If you can live with the trace width required for a ten-degree rise, you are good to go. If you want to try to skinny up the traces, ask for 20 degrees of temperature or more.

Q: 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?

The wagon wheels spokes are very short length traces and are heat sunk to the plane. The trace width calculator uses empirical formulas based on long traces with no special heat sinking. Generally, the wagon wheel spokes do not have to be anywhere near as wide as long traces. However, at this time, I don't know of a good way to do calculations for wagon wheel spokes.

Use our IPC-based PCB trace width calculator to estimate current carrying capacity and temperature rise before finalizing your layout.

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).

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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

This trace width calculator uses IPC-based models to estimate conductor width based on current, copper weight, layer location, and allowable temperature rise. It is intended to provide general engineering guidance, not final design validation.

Actual trace performance depends on many factors that cannot be fully captured in a simplified calculator, including:

Board stackup construction
Copper distribution surrounding the trace
Enclosure constraints and airflow
Ambient operating temperature
Thermal vias and heat spreading paths
System-level cooling strategy

This tool should be used as an early-stage validation and planning resource. Final trace geometry decisions should consider the full electrical, thermal, and mechanical environment of the board.

If your application involves high current density, confined enclosures, or high-reliability requirements, we recommend consulting with our Design Services or your regional sales representative before finalizing layout.

Learn More About Trace Width Calculations

If you would like a deeper technical explanation of how trace width calculations work, how IPC models estimate current carrying capacity, and when to add additional design margin, read our related article:

Trace Width Matters: How to Use a PCB Trace Width Calculator Effectively

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?

Trace Width Calculator

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