I know not truly CNC related but awfully handy… this website: https://www.blocklayer.com/
Has a lot of online calculators, now I can’t vouch for everyone they seem reasonable. One I am interested in is: Bar Board Spacing across Circle - Inch
This gives you the board count and lengths required to encompass a circle.
Now could I figure this out … sure, but this saves a huge amount of aggravation.