Saw a small display error. I cant edit now so I'll add the correction:

D/pi = C (where C = circumference)
that form is incorrect & should have read like this:
D/pi = C/pi = W (width in inches)
OR
C/pi = D (diameter in inches)

Calculations are all correct. That didn't change. Just fudged typed equation. My bad.

Any fellow computer science buddies, possibly MarkWatney, or other science or math people, can confirm.