Need a laser mathematician

If my laser has a beam of 1.48mm measured about 25 feet from aperture and the inner laser dot is 8.4mm measured with digital calipers at 30 feet what is the divergence? It is my RPL-225. It was certified at .892mrad divergence. I was wondering. I feel stupid but I don't know where to start with a formula. The 8.4mm was measured by me with digital calipers at 30 feet at my work.

Just enter your beam specs into this to find out what the divergence is.
http://www.pseudonomen.com/lasers/calculators/mRadCalculator.html

That's really good

nice link, thanks.