Where can I see exactly how many rads I have?

I found the solution while tediously studying the pip boy.
While it doesn't give an exact number, there is a gauge to the right of the main pip boy screen that reflects how much radiation you've contracted.

You cannot really determine it down to the exact rad, but should be able to guess to within 10 or so rads. As far as I can see, there is no rads bar or anything in the actual pip boy screen itself (as there was in FO3 or New Vegas).

If anyone finds it difficult to read the gauge, zooming in a bit (with the touchpad on a dualshock) makes it a little easier.
And as rpmerf commented, right click zooms on PC.