Hunter 101: is a series posts on The Hunting Lodge for the Hunter that is just starting out or is now returning back to the class. Each week we will review how you can help improve your skill playing a Hunter in WoW. So grab a desk, class is about to start.
I get a lot of emails from people asking my thoughts on Armor Penetration. I usually say the same thing over and over again. It’s worthwhile and for high level Marksmanship hunters it makes sense to stack it for the DPS advantage.
That being said, Armor Penetration is probably one of the hardest stats for hunters to understand
It didn’t use to be that way. Armor Penetration used to be strict reduction based on the percentage of ArPen you had. But in WoTLK we saw it morph like Hit and Critical Strike into a rating system.
This is where so many points of Armor Penetration equal a total percentage of ArPen. Great but makes for heavier and more complicated math and that only adds to the confusion. No wonder Blizzard decided to take it off of itemization table and bury it in Cataclysm.
That being said. You probably want to keep in mind some of the basic conversions and calculations I’ll use in this post.
Basic Armor Penetration Conversions and Formulas
Damage Reduction Formula
- Damage Reduction = Bosses Armor / (Boss Armor + 400 + 85 * (Hunter’s Level + 4.5 * (Hunter’s Level – 59)))
Level 80 Damage Reduction Formula
- Level 80 Damage Reduction = Boss Armor / (Boss Armor + 15,232.5)
Level 80 Armor Penetration Rating:Armor Reduction %
- 14 ArPen = 1% Armor Reduction
Armor Penetration Simple Explanation
So what is Armor Penetration? Simply put, the more Armor Penetration you have the more of the bosses armor you ignore.
Think of it this way. As a guy we have Athletic Supporters (Jock Straps), Soft Cups, and Hard Cups, Then we add external padding up to full fledged, “Give me your best shot you you can’t hurt me!” body armor.
Well, that’s basically how our bosses are. You still can do damage, but the more armor the boss has, the more is absorbed and the less damage you do.
Now as your Armor Penetration goes up. Well one of those layers goes down. The boss is still protected, but the shots sting a little bit more. See my point? (Of course there’s some high level mathmatical explanation that shows the direct correlation and how much you should stack but I think this explains it alright.)
Armor Penetration Explained in More Detail
So I gave you the basic explanation on Armor Penetration up above. And with all simple explanations it really doesn’t give the whole story. So let’s take another look what happens to Armor Penetration as other Debufs are applied.
As you can see having the warrior’s sunder applied it didn’t affect our percentage of Armor Penetration. All it did was make the ammount percentage less. In other words if you are at 10% ArPen before Sunder Armor, you’re still at 10%. It’s just that before Sunder Armor was applied you would ignore 1,300 armor points and now you’ll only ignore about 907.5.
Also understand that this stacks. So if you have other effects applied, your percentage will remain the same, but the amount of Armor Penetration you actually cause will shrink.
As armor debuffs are applied like the Warriors Sunder Armor, Druid’s Faerie Fire, and your Wasp’s Sting, the amount your Armor Penetration will be less. (See Below)
How do you calculate ArPen
Armor Penetration is actually a rating. Luckily for us there’s sites like Elitist Jerks, The Hunter’s Mark, Less QQ More Pew Pew, OutDPS and of course Warcraft Hunter’s Union, along with others that have done some extensive work on how ArPen gets calculated. So we don’t have to do a ton of back math and research here.
The actual ratio for ArPen Rating to Armor Rection Percentage is:
- 14 ArPen = 1% Armor Reduction.
Using the example above, we said the boss had 13,000 Armor and that our Hunter had 10% Armor Reduction. That means we had 1,300 ArPen Rating. Not too horribly bad, and considering that the cap is about 1,400, we’re doing real good.
The only issue of having this much ArPen is the tendency for people to forget their other stats like Crit and Hit. I still hold to my opinion as always. Armor Penetration is a nice stat, but it should never be a primary stat except in very specific circumstances.
Went to focus gearing ArPen
(There’s some debate on when you should really start stacking Armor Penetration over Agility. But here’s my understanding at the moment. For further clarification and calculations see Edit Note below.)
First, you need to be a Marksmanship Hunter. Why? Armor Reduction from Armor Penetration is really only effective with Physical Damage. So this means your Auto Shots, Steady Shots are actually hitting hardest. And typically Marksmanship Hunters have the hardest hitting Physical Damage in the game.
Survival hunters rely on buffs from “Spell” like Black Arrow and Explosive Shot where as Beast Mastery hunters work with their pets and use more Multi-Shot, Arcane and Serpent Sting. BM Hunters also partner with their pets more and ArPen isn’t a stat that doesn’t scale over to our pets.
That said, you’ll need to be a Marksman hunter.
The next is the actual “When?” to start stacking it. Well that answer is actually pretty simple really. Start “gearing” it as you get it. WAIT! Before you go out and say AHA! there’s a catch.
You can stack it as you get the gear for it, but I still reccommend that you don’t make a wholesale switch from Agility to ArPen until you’re getting close to the 1,400 ArPen cap or at a minimum around 900Arpen.
However, you can start considering geming ArPen instead of Agility at around the range of 400-500 ArPen (29-35% Armor Reduction). (See Calculations bel0w.) By this I’m not advocating a wholesale replacement because you’re not only losing Agi but also the Critical Strike Rating and Attack Power that goes along with it. All in all it seems that your DPS gain at 400ArPen looks to be about the same as 55 Agility.
(Note: You need to remember though Agility scales with buffs and ArPen does not. Also, remember that this is all based on the premise that you’re not dealing with other Armor reducing debuffs that also affect your own personal armor reduction ability. )
Let’s Recap
I think that about does it. I’m sure I left something out. But let’s take a quick review of what we learned.
- 14 Armor Penetration Rating = 1% Armor Reduction
- Hunter’s ArPen is applied AFTER all Armor Debuffs
- ArPen cap is about 1400
- Need to be a Marksman Hunter to consider stacking ArPen instead of Agility
- Need between 400-500 ArPen rating to start focusing gearing up for ArPen
- DON’T start “stacking” (replacing gems and etc..) until you’re at least 900 ArPen or higher.
So that’s it. I think pretty much everything you need to know about Armor Penetration and how to use it as a Hunter.
So do you stack ArPen? Do you feel it should be a primary stat for Hunter’s to use and min/max? Or do you think there’s already just too many stats and things to remember. Why not share your experiences below?
(I want to give a special thank you to Rilgon, Nassira, Fluffywumpkin, and Methuus for helping on clearing up any confusion on gearing ArPen over Agility. Thanks guys!)
EDIT NOTE:
(Thanks to ichi of Grey Area for helping to point out some errors in my math.)
It seems that there is still some confusion on why I say consider being between 400-500 ArPen to start stacking it.
First, anytime you start switching your choice of primary stats understand you’re making some pretty dramatic changes to your playstyle, buff and debuff requirements.
Also, I DO NOT advocate dropping all of your Agility as soon as you hit 400 ArPen. (I’ve edit my Hunter 101 post to help clarify this point.)
You need to carefully weigh the ± of each change. Nothing in this game is as simple as “Oh! I’ve reached x and it’s time to change everything to y.” This game just doesn’t work that way.
Anyways, below are my calculations that hopefully explain my conclusion of starting to stack ArPen when you reach 400-500 ArPen rating.
Remember here’s the Damage Reduction Formula:
DR% = Armor / (Armor + 400 + 85 * (AttackerLevel + 4.5 * (AttackerLevel – 59)))
Base Boss DR % = 13,000 / (13,000 + 400 + 85 * (80 + 4.5 * (80 – 59)))
Base Boss DR % = 13,000 / (13,000 + 400 + 85 * (80 + 4.5 * (21)))
Base Boss DR % = 13,000 / (13,000 + 400 + 85 * (80 + 94.5))
Base Boss DR % = 13,000 / (13,000 + 400 + 85 * (174.5))
Base Boss DR % = 13,000 / (13,000 + 400 + 14,832.5)
Base Boss DR % = 13,000 / (28,232.5)
Base Boss DR % = .460 or 46%
Adjusted Boss’ Armor w/ Hunter at 400 (28.57%) ArPen w/o Adjusted Armor Debuffs = 9285.9 (13,000 – (13,000 x 28.57%) = 9,285.9)
Adjusted Boss' DR% = 9,285.9 / (9,285.9 + 400 + 85 * (80 + 4.5 * (80 – 59)))
Adjusted Boss' DR% = 9,285.9 / (9,285.9 + 400 + 85 * (80 + 4.5 * (21)))
Adjusted Boss' DR % = 9,285.9 / (9,285.9 + 400 + 85 * (80 + 94.5))
Adjusted Boss' DR % = 9,285.9 / (9,285.9 + 400 + 85 * (174.5))
Adjusted Boss' DR % = 9,285.9 / (9,285.9 + 400 + 14,832.5)
Adjusted Boss' DR % = 9,285.9 / (24,518.4)
Adjusted Boss' DR % = .378 or 37.8%
±DPS% = Base Boss DR% - Adjusted Boss DR%
±DPS% = 46% - 37.8%
±DPS% = 8.2%
+8.2% DPS at 400 ArPen
Now to see the ± by removing Agility and adding ArPen.
Using Prawn’s EAP formula the Agi:DPS ratios is Appx. 1 Agi = ~.143 DPS. If this holds true, you would need to loose appx. 55 Agi to outweigh the benefit of ArPen.
-58*.143= -8.294 DPS
I will grant you this is all at a base level. If you add Agility related buffs and
Boss Armor debuffs you’ll see that everything changes pretty dramatically.
Because of this I again stress thay before you head off and drop all your agility gems make sure you take all the factors into consideration.
If you insist on doing a wholesale switch and not have any Agility you’ll probably need to be over the 900 ArPen mark as Rilgon points out in the comments.
I hate having to get to this level of detail in a 101 post but it seems necessary to make sure there’s a clear level of understanding for everyone.
(Edit: There was some confusion on the stacking of debuffs. Originally I had used the Rogues Expose Armor. And thanks to Fluffy for pointing out that Expose Armor doesn’t stack with Sunder Amor. So, I’ve changed that to Faerie Fire.
Also, I know there’s a lot of other guides out there on ArPen. However, some are not up to date and accurate though they do give some good insight on how ArPen works. Below are a couple of examples from other hunter bloggers. There are others as I mentioned above but this should get you started.
- The Hunter’s Mark: Hunters and Armor Penetration
- Less QQ, More Pew Pew: New Information about Armor Penetration
- Warcraft Hunter Unions: ArPen vs. Agi and MM Hunter Armor Pen Build
- OutDPS: Armor Penetration vs. Agility Redux )
Eddie Carrington “aka Brigwyn” is the owner/operator of The Hunting Lodge. He created The Hunting Lodge blog and Hunting Lodge Forums in response to players requesting a safe spot to talk about their class. Don’t forget to join Eddie on The Hunting Lodge Podcast that you can find broadcasting live on Ustream each Sunday at 11pm Eastern/8pm Pacific.
Eddie “Brigwyn” Carrington is often known as being that crazy dwarf on Twitter.
He's also a blogger, podcaster (Hosts Brigwyn's Corner, Co-host of Everything Blah! and of course Redneck Geek and Cajun Gamer with his good friend Andy "Daewin" Dino. 
Brig, I love ya, but there are a few gaping holes in your description/recommendations:
1) Expose Armor and Sunder Armor do not stack.
2) The general consensus (and my own spreadsheet modelling) seems to be that you shouldn’t switch from gemming AGI to ArPen until you are between 700 and 900 passive ArPen. With my current gear (no ToGC loot, just ToC25/ICC10 stuff), I sit at 495 passive ArPen. Regemming for ArPen is a net loss of 16 DPS fully raid buffed. Not statistically significant, but also not worth the expense (in Emblems or Gold) to regem.
For reference, here is the WHU page which originally discussed ArPen vs. Agi (http://www.warcrafthuntersunion.com/2009/07/hunter-armor-pen-vs-agility/) and an OutDPS followup (http://outdps.com/2009/11/06/armor-penetration-vs-agility-redux/)
Hey Fluffy!
I wouldn’t call those gaping wholes.
Actually, I’d say you’re recommendation is a bit dated on the Agility vs. ArPen links. And even though I got the stacking wrong on Sunder Armor and Expose Armor the explanation of the class mechanics is accurate. I’ll just swap out Expose Armor and put Faerie Fire in it’s place.
As for Agility vs. ArPen? Like I said your going off of information that’s a bit out of date.
Here’s the latest quote from Frostheim:
“In general I recommend switching to an armor pen model only after you have more than 400 or 450 passive armor pen (that is, without gemming or taking big gear downgrades to get the armor pen). At this point you should see an increase in your dps if you’re doing everything right.” from (MM Hunter Armor Pen Build – http://www.warcrafthuntersunion.com/2010/01/mm-hunter-armor-pen-build/)
Thanks for the comment though. I appreciate it.
Also I’ll make sure and include all the links at the end of the post just to help clarify any other confusion others might have.
Typically that seems to be in the range of 400-500 ArPen
Um… if you’re advocating gemming for Armor Penetration at a value THAT low, then I have to say that you’re 100% wrong in that regard. Now, if by “stacking” you mean “getting lots of gear with Armor Penetration on it”, then that’s a good thing to do regardless of your ArPen levels – more is better, and it gets better and better the more you have.
ArPen grows exponentially. Going from 1 ArPen to 2 ArPen is a huge difference compared to going from 1399 ArPen to 1400 ArPen. Every point makes the next point (up to 1400) better and better, which is both why you shouldn’t stack it until you’re nearing the hard cap, and why even small amounts are good because lots of the newer gear has it.
But yeah, gemming for it without a large amount of static ArPen is not wise. I have nearly 900 myself and it’s STILL a very slight downgrade to full-gem for ArPen.
I’ll have to respectfully disagree with being 100% wrong. Maybe I wasn’t completely clear and hopefully the latest edit notes will help clarify that point. Feel free to check my math and theory and let me know where I’ve gone astray but I think if you check the latest Edit Note you’ll see and better understand what I meant.
I’ll still hold to my 400-500 ArPen rating to start converting from Agi to ArPen as a base. But do concede that you’ll probably not see any realistic gains until you’re closer to the ArPen cap. (As now noted and clarified.)
Thanks for pointing out the need for clarification. Sometimes when trying to address the Hunter 101 audience things can get glossed over and maybe really shouldn’t.
I do appreciate the feed back.
All I know is this: In my current gear setup, I have 784 ArPen. If I remove my ArPen-proccing trinket for something else and calculate the weights of stats in Shandara’s 93f, I get 1.897 DPS for Agi and 1.919 DPS for ArPen – BARELY any better, and not good enough to replace 10 Agi/10 Crit gems in socket bonus-granting yellow slots, just good enough to replace 20 Agi red gems. The total gain there wouldn’t be much, either – only about 40 DPS.
Then, I use the manual stat mod tool to reduce my ArPen down to 450. Rerunning the stat calculation, I find that Agi is at 1.762 DPS per point, while ArPen has fallen hard to 1.641 DPS per point. The point at which ArPen and Agility converge in value (at 1.827 DPS per point) seems to be roughly 640 ArPen, but even at that point it’s STILL not worth it to do a complete ArPen regem – you only should be replacing your red 20 Agi gems with 20 ArPen gems, and you won’t be gaining very much at all.
It seems we’re in agreement though our numbers on when we see ArPen actually surpass Agility may be off a little and that seems to be more gear/buff related based on spreadsheet calculations.
Also, just to point out where we do agree. I stress a few times that I’m not advocating a wholesale swap of Agi with ArPen but to start adding ArPen instead.
If you’re looking at stripping gems and swapping gear pieces giving you a loss of Agility and replace that with ArPen you probably should be at least at 900ArPen or greater.
Thanks for the feedback. It’s appreciated as always.
I have to agree with Rilgon on this one. 450-500 is much too low to replace Agility gems. While the sources you’ve read are decent, the actual math is not there. Rilgon has calculated it, with the base being at 640, and you should not regem until then. And casual raiders: good luck getting 640 passive ArPen. Considering that many people who read this site are casuals, I have a feeling that a large number of MM hunters with 450 ArPen are going to start stacking their ArPen gems as a result of this post, and in turn, severely hurt their own DPS output.
I would suggest changing the 450-500 range to 650-700 to clarify for those who are less inclined to do their own comparisons. I think it would be more helpful to the overall hunter community.
@Nassira
I’m not sure if my wording is just not clear or if people are pulling a TLDR on the post. But either way I’ve tried to make it clear that I am NOT advocating for people to start pulling out Agility gems and putting in Armor Penetration. Actually, in the post I’ve gone out of my way to state this several times.
What I say pretty clearly if someone reads it is:
1. DO NOT switch all Agility to ArPen until you reach 900 or greater ArPen.
2. You can START gearing/stacking your ArPen around 400-500.
If my math is off in the post above I’ll be happy to correct it. But I’m sorry Nass but I think you misunderstood the post.
Well, but then that’s disingenuous wording, Brig, because you can start “gear-stacking” Armor Penetration at any time. Building a solid ArPen foundation is a great move for any MM Hunter, and is fairly decent for SV Hunters as well.
The term “stacking” has funny connotations. When I see “stacking”, my brain immediately says “stick $STAT in any available location, including gems, enchants, flasks, and food”. Perhaps “gearing heavily for ArPen” would’ve been a better wording? It certainly wouldn’t have caused me to start this comment chain, that’s for sure.
I have to agree with the others. The word “stack” when referring to gems is usually taken to mean “replace every single gem (except meta and a nightmare tear) with this type”.
If you’re using a different meaning for “stack” then you need to clarify that in the post.
Thanks, Brig. I do think you should change the wording and have it be more clear as to exactly when a hunter can do what. Between gems, extra buffs like food, and gear, “stacking” is too broad a term for what you’re thinking. If I were you, I’d go ahead and differentiate between all three of those, taking care to say “This is when you can effectively re-gem, this is when you can add buffs, and this is when you should be collecting the gear (which, gearwise, is always, for MM – if there’s a choice between a piece with hit and a piece with arpen, generally you want to be taking that arpen piece).
Thanks for understanding that I’m not trying to be a douche. lol <3
@Nassira
No thank you!
The one thing I don’t want is for people to walk away saying, “That Brigwyn guy from The Hunting Lodge said I could replace all my Agility gems and now look! Geez! What a lamer!” lol
And you a douche? I’d never think that.
You’re too full of awesomeness! 
Wow.. this should be stickied in the Hunter Forums..
This is like the.. MM Hunter’s Bible.
But I too sorta question the armor penetration socketing. I won’t really know until I see it for myself.
I too am at 780Arm Pen. And I am seriously thinking about socketing a couple Arm. Pen gems.. but I still don’t know what I want to do.
But this site certainly helps. Thanks a bunch
Good info, one error that processes into a big difference
Adjusted Boss’ DR% = 9,285.9 / (9,285.9 + 400 + 85 * (80 + 4.5 * (80 – 59)))
Adjusted Boss’ DR% = 9,285.9 / (9,285.9 + 400 + 85 * (80 + 4.5 * (31)))
80 – 59 = 21, which rewrites the subsequent equations
9285.9/(9,285.9 + 400 + 85 * (80 + 94.5))
9285.9/(9,285.9 + 400 + 85 * (174.5))
9285.9/(9,285.9 + 400 + 14832.5)
9285.9/24518.4
0.378732
±DPS% = Base Boss DR% – Adjusted Boss DR%
±DPS% = 40.6% – 37.87%
±DPS% = 2.83%
+2.83% DPS at 400 ArPen
if I am incorrect, please forgive me
Is that egg on my face or am I trying to make an omelette?
Okay, so at 400 it seems to be a +2.8DPS instead of the +7.8.
It’s still an increase just not nearly as much as I had first thought. In some ways it even makes even more sense to hold off on “Stacking” ArPen until you’re closer to the cap.
Thanks a bunch, I’ll make the edits and note your comment.
Okay, I went back and looked to see what the difference was. Since I had the same error calculating the base DPS as well as the Adjusted DPS it actually caused a small increase in the DPS.
(Well, unless I did yet another math mistake. And if I did please feel free to point out where b/c I’d like to make sure this is as accurate as I can get.)
Thanks again for all the help!
Thank you for all that you’ve done for me