Calculator tools

Hello I am trying to configure the track width with the Calculator tools. And there are two dimensions in ‘‘Track Width’’ : Trace width and trace thickness.
Is here the track default to be rechtangle ? What if I am using a round track ?

Thank you :slightly_smiling_face:

Are you confusing pads and tracks? What is your idea of a track?

It’s a bit weird that KiCad’s calculator uses “Trace width” in this context. Tracks and traces are both the same thing on a PCB, but KiCad apparently standardized on the “track” nomenclature. KiCad even calls it a Track Width calculator in the menu.


This is about the cross section of the copper. PCB tracks are always rectangular (or slightly trapezoidal). Round wires are not used on a PCB. The calculator will also not work properly for calculations on round wires. First the PCB has a cooling / heat spreading effect and this is especially noticeable on thin tracks ( A 0.3mm thin track can already handle 1A! And second, the thick insulation of regular wiring also has a heat insulation effect so the wire gets even hotter.

Hello, as I know trace or track is wire on PCB board.

So why do think they could be round?

I thought it so because I mixed the PCB track with the normal cable, my bad. Sorry :sweat_smile:

Ahhhh, I have been wrong all along. But if so, why in Board setup - Constrains or Netclass there is only ‘‘trace width’’ while no options for ‘‘trace thiness’’ ?

Track thickness is determined by the thickness of copper, which is normally expressed as weight per unit area, e.g. 1 oz, 2 oz. It’s not something you can change from area to area on the board. It’s when you design the circuit you have to be aware of the resistance of the track, whether it matters and the heat generation and order sufficiently thick copper, or widen the tracks. That’s what the calculator is for.

Thanks, so the track thickness equals to the copper thickness ? Where can I find out the copper thickness in PCB editor ?

It’s not specified to the PCB editor. Rather you tell the manufacturer in your order. I think advanced production formats can carry this information but those formats are not in widespread use, so most people specify it in the order. Just look at a typical order form, it will have 1 oz, 2 oz, copper etc. For the vast majority of designs 1 oz is sufficient. More will cost extra, of course.

So, I have to choose the trace width without konwing the thickness at the very begining ? So how can I be sure I am using a suitable track width for a certain current ?

The thickness of standard 1 oz copper is 35 μm so you start with that figure. Then you see if the temperature rise for high current tracks are acceptable. If not, increase the width. If you run out of width then you increase the copper thickness and pay more. Besides the temperature rise there will also be voltage drop.

Thanks :grinning:, and as I know, the length of a track could also influence the impedance of it, which means that for a certain current, with a different length there could be a different suitable width, but I won’t know the length before the routering is finished. So what’s the proper strategy for this issue, how can I select a suitable trace width without knowing the length of it ?

Let’s go back to basics: a copper track is like a resistor: a current will cause an increase in temperature. You need to decide how hot you can let it get, how much current you need it to handle, and what thickness (also called “weight”) of copper you will use when the PCB is made.

That is enough detail for a track calculator work out the width of track needed. You may want to get figures for different “weights of copper” (1oz, 2oz etc) so you can choose from the suggested widths. If you are struggling to get a narrow enough track, then revisit what temperature rise you can accept (keeping in mind safety etc)

1oz copper is the norm, anything thicker will cost more, and may take longer to be made.

There is

Only when you are working with high current or high frequency do you need to worry much about length and width. Generally you try to minimise length by suitable placement and routing. Then see if the chosen width is ok. For my designs I usually have only two widths, one for power tracks and a default for everything else. But then my designs are not demanding.

Width has really nothing to current.
If your track is 2 times longer than (with the same current) energy released in it will be 2 times higher but also heat dissipation surface will be 2 times higher. The effect is that temperature rise is the same.

Do you suppose that based on iron current need you decide that you can connect it only to socked close to electricity meter but can’t connect to socked in the farthest room when all cables used are the same?

Click the Green Icon at top left of the PCB Editor Panel…

A 1inch (25.4mm) long Track of 1mm width is set/shown below, along with Calculation from a Plugin I wrote showing good correlation…

Ahhhh, thank you very much :grinning: