I’m attempting to hand make a edge cut of a Acute isosceles triangle, I’m getting bit by KiCad’s precision I think, base of 67.99mm with sides of 60.08mm, that comes out to a angle of 55.54d on the bottom corners, KiCad is doing some rounding here as I’ve got a 0.88mm error at the point ( https://i.imgur.com/b3Ludtu.png ) with “Move Exactly” its rounding my rotation to 55.5? and causing the slight angle here

Using the angle isn’t the primary way to manipulate lines in KiCad, it’s just calculated using the endpoints. For some reason v5.1 limits angles to one decimal. It’s more accurate in v5.99 but it’s still an approximation unless it happens to result to exact coordinates, I think.

It does have plenty of internal resolution for coordinates. It works with 32bit integers and nanometer resolution. which gives PCB coordinates of around -2 meters to +2 meters.

There is rounding for angles (I think rotation is rounded to 0,1 degree), but not for coordinates of endpoints of lines and circle segments.

So the obvious workarounds are either to calculate the coordinates in some other way, or use a mechanical CAD program to draw your thing and use a DXF import to get it into KiCad.

The difference of 55.5 - 55.54 = 0.04mm and the thickness of an average human hair is 0.08mm

The tolerance on manufacturing/cutting a PCB by any fab house will be much larger… and, you’ll pay $$$ for that kind of accuracy (if you can find someone to comply)…

that’s not a good reason not to have perfect precision in the design. and like OP said, his actual positional error is 0.88mm, well above the +/- 0.2mm tolerance most places quote.

this is a bug that should be fixed. the proper way to handle this is to round values for DISPLAY so people aren’t overwhelmed by useless decimals, but full precision is maintained internally.