Here's an online version that does pretty much the same thing.
This isn't mine, but it hasn't picked up alot of steam on the Warrior forums from the guy who posted it (probably because he did it on an alt and everyone assumes the link is a keylogger).
Nice veneretio. Tankingtips is your own website?
Oh, and from the WoW-US forums:
I tried it, and yeah, it goes negatives with lower levels. May be a PHP issue depending on how it is set up.um....im a lil skeptical, if i set enemy level to 50 my effective health is 220,168 but if i set it to 45 my effective health is -204,790 (yes negative)
Ya as I mentioned on the us forums. It is not intended to work for level 1-59 since that uses the following formula.
%Reduction = (Armor / (Armor + 400 + 85 * Enemy_Level)) * 100
Where as level 60 and up uses...
%Reduction = (Armor / (Armor - 22167.5 + 467.5 * Enemy_Level)) * 100
So you can definitely see that when the enemy level is too low for that formula you'll end up with a negative reduction percentage.
And yes tankingtips.com is my site that I've been putting together over the last couple months since I got tired of losing information and having to re-find it again and I found myself explaining concepts over and over again to guildies and friends alike. Suffice to say between a full time job, a life and a wow addiction it moves forward slower than perhaps I'd like
I updated the calculator noting what formula I used. I think you'll find that it should be perfectly accurate (rounding the decimals off) for level 60 and up mobs.