The ACTUAL attack and block chance

[Zac26]

So i was wondering if someone could better explain the mathematics behind the attack and block chances, because a 100% chance in the game obviously does not mean that you will actually hit or block 100% of the time. I'm assuming its based on the respective ratios of the attack chance of the attacker versus the block chance of the blocker but i have no info on how it actually works.

[rijackson741]

It's based on the difference in attack chance and block chance. It works the same way whether you are attacking or the monster is attacking. If the difference in AC and BC is C, then the actual chance to hit, F, is

Chance to hit formula.png

Here's a graph to show how that works:

Chance to hit graph.png

The blue curve is the chance for the attacker to land a hit given the difference in AC and BC. So getting a chance to hit of more than 90% is unlikely, but so is getting a chance to hit of less than 10%. This applies to you and monsters.

The red curve is the rate of change of the chance to hit as a function of the difference between AC and BC (i.e. it's the derivative of the blue curve). I added this because it's quite instructive. If you add AC, the biggest benefit you get is when your AC is 50 higher than the monsters BC, where the derivative is a maximum. Also, when you add BC, the biggest benefit you get is when your BC is 50 lower than the monsters AC, also at the maximum of the graph. If you already have a high AC relative to the monsters BC, then adding AC will not get you that much (at the high end of the graph the derivative is small). That's something you might have expected, but there a flipside to that coin that you might not have expected. If you have a very low BC relative to the monsters AC, then adding BC will not get you that much (at the low end of the graph the derivative is also small)! So if you have a very low AC or a very low BC, you have some work to do, and initially you will not get much for your efforts

[Zac26]

This is perfect, thank you.