Easily one of the most misunderstood skills, and for good reason. The formula behind it is complicated, and on top the that, the effective AR of each shield depends not only on it’s Base AR value and magic modifiers, but your Parry skill as well. Luckily the formula is a lot simpler when your Parry skill is 100, as it should be if you plan on using this skill. First we’ll start with a table of shield Base AR values.
Buckler 7 Wooden shield 8 Bronze shield 10 Metal shield 11 Wooden Kite shield 12 Metal Kite shield 16 Heater shield 23 Order 30 Chaos 32
Start with the Base AR.
If the shield is exceptional, add 8
If the shield is magic, add 10, then add the following values for magic level.
Defense 5 Guarding 10 Hardening 15 Fortification 20 Invulnerability 25
This number is the AR of the shield.
For example, a Bronze shield of Defense would be 10 + 10 + 5 = 25
Now this is where it starts to get a bit more complicated. You now have the AR of the shield. But it’s Real AR is modified by your Parry skill according to this formula:
((Parry * AR) / 200) + 1
If your Parry skill isn’t 100, feel free to plug those values in and figure it out. But assuming you’re doing it right and have 100 Parry, the formula is a lot simpler:
(AR / 2) + 1
So for our Bronze shield of Defense from the previous example, it’s Real AR at
100 Parry would be:
(25 / 2) + 1 = 13
So our real AR is 13 (the division always rounds down). Now that we know that, we can calculate our Parry chance. This is the actual chance we will block the damage with our shield. It is based on our Parry skill and the Real AR value we just calculated.
chance = (Parry – (Real AR * 2)) / 100
So basically, we subtract double our real AR from Parry skill. With 100 Parry, we get
chance = (100 – 26) / 100
chance = 74 / 100
So we have a 74% chance to block the damage with our shield. But what happens when we block that damage?
If the incoming damage is from Archery, we use the full AR of our shield. So:
damage = damage – AR
But if the incoming damage is Melee, we only use half the AR of our shield. So:
damage = damage – (AR / 2)
In this case, a successful Archery parry would block 13 damage, and a successful Melee parry would block 6 damage.
Parry could be a useful skill, given the right equipment. With the numbers in front of us, we can see that any magic shield is much better than an exceptional one. An exceptional shield only gets a +8 AR boost, the lowest magic shield, defense, gets +15. Since shields cause no dex loss, there is no advantage to making them out of colored metals. So the question is, which shield to use?
The tradeoff is apparent. The higher the AR, the lower your chance to block. For every point of AR, you lose 2% chance to block. However if you study the formula you will see that, for melee attacks which are by far the most common, we only use 25% of the original AR of our shield! So our 25 AR bronze shield of defense only blocks 6 damage.
Here’s a quick way to calculate the block chance and actual damage blocked. Do the initial AR calculation, starting with the base AR and adding any exceptional or magic bonuses. For our bronze shield of defense, that was 25 AR. That is roughly how much percentage to block chance we lose from 100%. 100% – 25% = 75%. Not exact but very close.
To quickly calculate how much damage is blocked, take that same AR value (25 in this case). If it’s an archery attack, halve it. If it’s a melee attack, divide by 4. That’s how much damage will be blocked. In this case (25 / 4 = 6) it’s right on the money.
Looking at the harsh AR penalty (damage reduced is AR / 4), it might seem better to use the highest AR shield available. You may get hit a bit more, but the damage blocked will be worth it. If we look at the highest AR shield available, an invulnerability heater shield..
23 + 10 + 25 = 68
We only block 32% of the time, (100 – 68)
When we do, we are blocking 16 damage. (68 / 4)
It actually scales quite evenly. We almost triple our damage blocked (6 -> 16), and reduce our chance to block by almost 1/3 (74% -> 32%). So in the end, which shield you choose depends on whether you are getting a lot of small damage amounts (horde of weak mobs), or a big hits from one opponent.