Calculation of Trace Width

Thread Starter


Joined Feb 5, 2013
Hello All,

This forum always useful for me to get experts help.. Thanks for creating this forum.
Now Que:-
I am working on PCB design, and used Auto Routing tool for routing(As preffed by my company). I used all trace's width 0.25mm. Is it okay? and I have to increase trace width for +5V, +3.3V and Ground Plane. How can I calculate those trace width.

Thanks in Advance


Joined May 11, 2009
Thank for your reply.Still one question remain unanswered rest of trace width 0.25mm is fine??
It depends, without knowing anything about current, voltage or temperature requirements. We can not give any answer than maybe. Make an estimate and the use the Trace Width Calculator.:)


Joined Sep 20, 2005
0.25mm is 10mil, which is a typical figure, but this really depends on the tolerances of your board manufacturer.
I usually use 24mil, 32mil or even larger for the power traces for logical circuits. Power stuff usually calls for much larger traces, say 60-80mil for upto few amps. Also, thinner traces have larger inductance, which can be important in some circuits.


Joined Feb 25, 2013
Just as an example... the board I use is 35 micron or 35um copper. A circuit with a current draw of 1A would require 0.3mm tracks. So in answer to your question, if you are using 35um copper and assuming the room temperature is 25 degrees C, with trace widths of 0.25mm you can draw 875mA.


Joined Sep 20, 2005
A circuit with a current draw of 1A would require 0.3mm tracks
That is for a 10 °C rise on internal layers (inside a 4 and more layer board). If you can allow for example 30 °C rise in the temperature of the traces, the required width gets smaller.
For the 30°C rise on outer layers the calculator gives me 6mil traces, but I wouldn't dare to go so thin.