If you press and hold the left mouse button over the toolbar icon, you’ll see more tools:
If you want to know the sum of lengths of selected track segments, then you’ll have to use one of the plugins currently.
If you select a single track segment, then the message bar will show something like this:
You’ll usually want the “Full Length” from the first variant and “Router Length” from the second.
The lengths in the tuning tools are calculated by finding point-to-point paths (from one pad/junction/end to another). It’s important that the connections are exact, otherwise you’ll get miscalculations (use U to check).
If you presume you have a point-to-point path, but the length in the message bar doesn’t match the length shown in length tuning tools, then usually there’s a stub somewhere along the track line, or the connections are not exact.
Both the message bar and the length tuner calculations will clip the track segments that are coming in/out of pads, and add the via lengths based on distance between corresponding layers.
On the contrary, the Net Inspector dialog will just sum up all track segment lengths and via heights.
Tuning path of the length tuner shown as a blue line:
If the track doesn’t connect to the pad center exactly, an incorrect path will be used:
Track length plugins are useful for cross-checking the length tuner calculations (also be aware of via heights)
If you want to see the path the length tuner is tuning (graphics like in the above screenshot), you can create a text file named kicad_advanced (without extension) in %APPDATA%\kicad\6.99 or %APPDATA%\kicad\6.0 folder and put this content in it, then restart KiCad:
ShowRouterDebugGraphics=1
