Here's a little tool, something that I've wanted to do for a while but never quite got around to. It's the javascript equivalent of one of my posts: I start out with the intention to write something nice and simple. Then I get fascinated and pulled in deeper than I planned. Oh well!

It's a calculator for Power Word: Shield. The simplest way to use it is to plug in your spell power and hit calculate. You can also add a “booster,” which is used to mimic the T10 set bonus (5%) and/or the ICC zonewide bonus (5–30%).

(Until I see math indicating otherwise, I'll assume that those bonuses are applied after the normal shield value is calculated. Please link if you've done or seen this math!)

You can also compare two shields. E.g., how much of a boost would your shields get from an additional 100 spell power? The comparison shows both hit points and percentages.

The formula and some useful resources are below.

Here is the formula. For simplicity, I've assumed you're fully talented into all relevant talents.

PWS = (Base+(SP*(coeff+BT)))*(1+TD)*(1+FP)*(1+IPWS)

Base = 2230 for max rank

SP = your spell power

Coeff = 0.8068 (the spell power coefficient)

BT = 0.40 (5/5 Borrowed Time)

TD = 0.05 (5/5 Twin Disciplines)

FP = 0.04 (2/2 Focused Power)

IPWS = 0.15 (3/3 Improved PW:Shield)

Now, whether or not the formula is working as intended is an open question. The comments and bug reports on the WowWiki page are very interesting. That page also lists some tips for using PWS, as well as the history of PWS in patch notes. Highly recommended reading.

Also, Zusterke has a full-featured priest spell calculator. It does much more
than this page ever will, including the ability to take less than full ranks of the relevant
talents. It also does *all* priest spells, and works for (gasp!) holy priests too. It's
a fantastic resource.

Are the ICC & Set bonuses additive? i.e. can you just plug in 10% for both?

I would assume they're multiplicative. In other words:

(PWS) * (set bonus) * (Zone bonus)

So for a 5% set bonus (1.05) and a 5% zone bonus (1.05), your net shield would be

(PWS) * (1.105)

Which amounts to a net 10.5% bonus. When the zone bonus goes to 15%, you'll see a net bonus of (1.05)*(1.15), or 20.75%.

Thanks for the post m8, quite a nice calculator.

I'm thinking about launching my blog soon, just made a post which extends your math with the T10 4p. I'm curious what you think about it.

Cheers

Oh, error number 1, posting the link.

okay a couple of things here. 1) the 4pc dosen't actually give 5% bonus so maths are going to be a little bit off. Also since you are using the wowwiki formula it is off by about .76%-.79% this is assuming that twin disciplines does in fact give x2 (so a total of 8% bonus from twin disciplines on yourself) bonus. This is due to some random modifier or something, and increases with spell power. But other than that these are nice estimates.

-Entrop

i guess i shouldnt have numbered seeing as how i forgot to add a 2) lol anyway.

Hi!

I posted something similar 5 months ago!

Guess no one read it.. :(

http://penancepriest.blogspot.com/2009/12/crit-vs-haste.html

Check the comments on your post..

I graphed my results, it gets interesting :)

Your calculator seems to get the same results as i did.

greetings