The formulas at the top of that webpage are having trouble representing exponents.toggle quoted messageShow quoted text
Probably got lost when scraped up with a copy and paste from some other source.
For example: "Note that many other manufacturers quote AL as nH/t2 for both types of material. "
That should read AL=nH/(t**2) where t**2 is the number of turns squared.
Also: "Ferrite: turns = 1000 ((desired L/AL) 0.5) (where L in mH) "
should be turns = (1000*(mH/AL))**0.5) = sqrt(1000*(mH/AL))
But otherwise, a good source of info on torroids.
Here's a very interesting writeup on the sorts stuff that go wacky when using torroids: