Is it possible to set cscaling factor in Illustrator?

Hi there,

I have a diagram that i am drawing in 1/4 ration (e.g., if the original length is 20cm, then it's i willdraw as 5cm). When I draw the line, I can use the Line Segment Tool Options and type 20/4 and it will automatically calculate the value for me, which is very handy,. However, sometimes I need to measure the length of a path, so I enable the Ojbects option in the Document Info panel, and it shows me the length of the selected path, which is great. However, the lenth is shown as the calculated value, which makes sense because that's the actual length being used. However, I wil hae to use a calculator and convert the value back each time I want to look up something. Is there a way to set something like scaling factor for a document so that I don't have to do this conversion back and forth? I tried to look up settings in the document, artboard, or the preferences but couldn't find anything. Is there a way to do this? Thanks in advance.