How to draw lines with irrational lengths and rounding edges

I would like to draw a line (and generally work) with a irrational length, like sqrt(2) or etc. Is it even possible?
For example - now I am trying to round this edge and I know that I need to have 4 mm thickness in the narrowest spot (see img). This was everytime pain to me to do something like this, commonly I was doing it like “eh this look good, lets connect the ends to the surface and it will somehow works” (I am (trying to make :D) making models for 3D print, so minor errors and imperfections are not an obstacle). Now I know where have the ends of e.g. 2 arc function but I don’t know how to measure it and ,deposit".

Thank you for response!

Generally I would like to draw a circle while I know the distance between A and B on picture bellow.

One rather simple way is to use the ‘Tape Measure’ tool inside a group.
Isolate (or copy to the side) the relevant edges (both legs), the circle, etc. of the current situation to have them in a separate group. Now inside the group measure the distance A-B and type 4 and answer the question about resizing the active group or component with yes.

Something like this:

You now have the correct arc to replace the former one.


with 1001bit Standard

Thanks, it works :blush: Finally I can do this rounding precisely and normally :smiley:

I am not sure if it is possible to add extensions to Free online Sketchup, but even so thank you for response.