# How to calculate binocular overlap

I have two cameras of which I know focal length, principal point, rotation and position. The cameras are in an ideal parallel stereo system.

I want to know with as few calculations as possible how much the images of these cameras overlap (let's say a percentage).

I am trying to follow a guide called Creating correct stereo pairs from any raytracer, but I cannot find how to set aperture and eye separation to find delta.

Can I do it with my current data? Or is there a better way to know how much the camera images overlap?