I found some interesting Javascript for doing conversion calculations.

It has a nice Inductor and Capacitor feature for when you can't remember which way
to move the decimal point. :-)

I was looking from some info on Toroids and the number of windings.

/content/toroid_turns.htm

I liked the toroid info that I made a screen capture of the info from the website.
The credit to the original author is listed above the image. I have gotten burned
in the past were someone has great info and then their site goes dark. Making a screen
capture like this solves that problem.