Is there a way to zoom on screen to actual size?

 From:  Matadem
11799.1 
Good day.
This might a weird one...but is there a way to zoom to actual size?
so let say a circle is 50mm and on screen it is actually 50mm?

I am making a metal flange and I just want to put the gasket on the screen to see how close I am.

Tnx!