# How to calculate PCB track width on proteus?

The current in my circuit is 60A and voltage is 36V. How wide should the tracks on my PCB be?

• I am not sure about Proteus, but there are numerous online calculators. PS 60 amp track will be super wide! – Tyler Mar 3 '19 at 15:01
• For traces on 2 oz copper board at 10 degree temperature rise from 25 degrees ambient, you'll want 111mm wide internal traces and 42.6 mm wide external traces. For 4 oz copper board, half that. Perhaps consider using wires instead. – K H Mar 4 '19 at 4:29

You'll need it wide, and thick if you can (2 oz copper vs 1 oz copper). There are calculators like this one https://www.4pcb.com/trace-width-calculator.html that take into account current, copper thickness, allowed heat rise, internal or external trace, trace length into account and calculate a trace width. Other board houses have calculators also.

If you do this, you will melt the track

simulate this circuit – Schematic created using CircuitLab

This is not determined by board houses or PCB design software, but by IPC standards. IPC-2221A Section 6.2 states:

The minimum width and thickness of conductors on the finished board shall be determined primarily on the basis of the current-carrying capacity required, and the maximum permissible conductor temperature rise.

The formula provided in the standard is:

$$I=k\Delta T^{0.44}A^{0.725}$$

where:

• $$\I\$$ is the current handling requirement in amperes
• $$\\Delta T\$$ is the allowed temperature rise of the trace in degrees Celsius
• $$\A\$$ is the the cross-sectional area of the trace in square mils
• $$\k\$$ is a constant which equals 0.048 for outer layer traces, or 0.024 for inner layer traces.

The cross-sectional area is determined by your trace width and your copper weight (measured in mils, millimeters, or oz/ft^2). If you don't want to do the math by hand, there are certainly plenty of calculators out there on the net. My point is that it is not a custom value depending on your board house, your design software, or anything of that sort. They will all point to this formula, so I simply prefer to skip the middle man and calculate the required trace widths myself from the start.

• That formula does not depend on trace length, but a long trace will get hotter than a very short one. – Uwe Mar 4 '19 at 20:44
• @Uwe Source? You may be right, but the formula used above is what is called out in what can be considered THE bible of PCB design. – DerStrom8 Mar 4 '19 at 22:12
• If it is a good bible of PCB design, there should be some sentences about the conditions when this formula is applicable. A large PCB filled with a high current coil with many windings would get much hotter than calculated. – Uwe Mar 5 '19 at 11:04