Unity - Top Down Perspective Camera to Orthographic size

I have a perspective camera with an fov of 60. It looks at an object from top view with a rotation(90, 0, 0) and position (0, 50, 0)

The user has the option to change the camera to orthographic view to get a 2D view without any depth from top

Now how can i calculate the orthographic size so the view looks same as that in the perspective view(just not having the depth)?

  size
--------
\     | d
\    | i
\  f| s
\ o| t
\v|
\|


size / distance = tan(fov) using SOHCAHTOA

size = distance * tan(fov)

So the orthographic size should be set to distance * Mathf.Tan(Mathf.Deg2Rad(fov)) where distance is how far away the camera is from the object it's viewing (in your case, I believe 50).

If you know that you won't change the FOV, and/or you know the distance, you can pre-calculate it. For 60 degs and 50 units the orthographic size will be 86.6025403784.