TL;DR: press the space bar to set the origin of the relative coordinate system and then watch the dx,dy cursor coordinates in the status bar as you draw.
See section 2.6. “Displaying cursor coordinates” of the Eeschema reference manual.
There are two coordinates systems (frames) in KiCad:
- absolute: origin is in one of the corners of the “paper” sheet, displays as “X…Y…”
- relative: origin is wherever you set it using the space bar, displays as “dx…dy….”
KiCad continually displays the location of the cursor in the right side of the status bar which appears near the bottom of the application window. KiCad updates the displayed location even as you use some tool to draw, place, etc. KiCad displays the location of the cursor in both coordinate systems.
Use the relative coordinate system to layout a board mechanically. First set the origin, say to the upper left corner of your board:
- move the cursor to where you want it
- press the space bar. Expect the relative coordinates to change to “dx 0.0000 dy 0.0000.”
Then as you draw, you can stop the cursor at some precise dimension.
KiCad does not persist the origin of the relative coordinate system (save it in your project.) You need to set the origin at the beginning of each design session.
KiCad does not display any particular symbol at the origin of the relative coordinate system. You can add a fiducial symbol at the origin.
Few people use the absolute coordinate system and many people complain that you can’t set its origin. But they should just use the relative coordinate system.
From a user-interface viewpoint, maybe KiCad should:
- place more emphasis on the relative coordinate system (display relative coords left of/preceding the absolute coords)
- make the origin persist
- add a pop-up menu item to set the origin (space bar is too obscure)
- make the displayed nomenclature more consistent (why is it not “dX,dY and dx,dy” or “X,Y and x,y” or “aX, aY and rX, rY” or “abs x,y and rel x, y”)