understanding critical hits

[Slapphappy]

My toons are reaching a level where critical hits are starting to matter a little more. Can someone help me understand the math behind this? How are critical hits rolled and 'confirmed'? What stacks and what doesn't?
How do items like 'keen' and 'seeker' affect this?
How do enhancements like 'fighter critical accuracy' work?
What about feats like 'power critical' and 'improved critical'?

Finally, is it worth investing in critical hits and, if so, what is the best wat to do it?

[jkm]

How are critical hits rolled and 'confirmed'?

each weapon has a critical hit range based on the natural d20 to hit roll. if the initial roll is within this range and you hit the mob, then you threaten a critical hit. a confirmation roll is then performed. on this roll you just need to hit the mob to confirm.

for example, you have a rapier with an 18-20 critical range.

a) you roll an 18 on the first roll but miss. no critical hit
b) you roll a 19 on the first roll and hit. you roll a 1 on the confim roll (auto-miss). damage is rolled as a non-critical hit
c) you roll a 19 on the first roll and hit. you roll a 19 on the second roll and hit. this is a critical hit and uses the multiplier
d) you roll a 19 on the first roll and hit. [not sure if this is rolled, btw] you roll a 20 to confirm (auto-hit). however, the target is immune to critical hits (undead, etc). damage is rolled normally, however all critical effects are applied to the mob (burst, enfeebling, puncturing, banishment).

[jkm]

How do items like 'keen' and 'seeker' affect this?

keen doubles the critical threat range of a weapon. in essence, giving the player improved critical for that weapon. it does not stack with improved crit however.

example - a greataxe is 20/x3, a keen greataxe is 19-20/x3

seeker - adds both a bonus to the confirm roll and adds the seeker bonus to the damage of the weapon before the multiplier.

example - a +10 seeker light pick 1d4 20/x4 would have an additional 40 points of damage on a critical because of the 10 seeker being added to the x4 multiple.

[jkm]

How do enhancements like 'fighter critical accuracy' work?
What about feats like 'power critical' and 'improved critical'?

critical accuracy and power critical only affect the confirmation roll. improved critical doubles the threat range of the weapon like keen.

improved critical examples
rapier 18-20/x2 with impr crit: pierce becomes 15-20/x2
kopesh 19-20/x3 with impr crit: slash becomes 17-20/x3

the confirmation roll is as follows:

d20 + normal to hit + seeker bonus + power critical (+4) + critical accuracy enhancement

where the enhancements become key is when you are only hitting near the crit range.

example assumes +6 seeker, power crit, and +4 critical accuracy enhancment

you only hit on an 18+ with a rapier. this threatens a critical. the confirm roll hits on a 4+.

[jkm]

one thing that wasn't asked was about the damage from a critical. critical damage uses the following formula:

(base weapon damage + damage from feats + damage from enhancements + str modifier (1x for one handed 1.5x for 2 handed) + seeker modifier + damage from buffs) x critical modifier + other weapon effects

[jkm]

Finally, is it worth investing in critical hits and, if so, what is the best wat to do it?

this is a build decision. crits are important to achieve max damage (whether it be stat damage or physical damage). as such, some classes favor criticals more than others.

there are only 4 ways (that i know of) to improve the occurance of criticals:

1. use a weapon with a high critical threat range (rapier, kukri, SoS, etc)
2. take the feat improved critical to double the threat range
3. use a keen weapon if you don't have impr critical
4. be a barbarian and take the enhancement to add to the critical threat range

everything else is related to making the critical stick.

[Slapphappy]

This info is very helpful. I think I will invest in the improved critical feat and not worry about the rest.

[sirgog]

This info is very helpful. I think I will invest in the improved critical feat and not worry about the rest.

Good idea. You won't regret taking that feat.

[Hence]

The power critical feat is pretty pointless imo. You can crit and roll a 1 on the confirm and still do full crit damage. A roll of one is not an auto-fail for a confirm critical roll.

[Aranticus]

How are critical hits rolled and 'confirmed'?

each weapon has a critical hit range based on the natural d20 to hit roll. if the initial roll is within this range and you hit the mob, then you threaten a critical hit. a confirmation roll is then performed. on this roll you just need to hit the mob to confirm.

for example, you have a rapier with an 18-20 critical range.

a) you roll an 18 on the first roll but miss. no critical hit
b) you roll a 19 on the first roll and hit. you roll a 1 on the confim roll (auto-miss). damage is rolled as a non-critical hit
c) you roll a 19 on the first roll and hit. you roll a 19 on the second roll and hit. this is a critical hit and uses the multiplier
d) you roll a 19 on the first roll and hit. [not sure if this is rolled, btw] you roll a 20 to confirm (auto-hit). however, the target is immune to critical hits (undead, etc). damage is rolled normally, however all critical effects are applied to the mob (burst, enfeebling, puncturing, banishment).

the confirmation for the critical hit is a check. checks do not fail automatically on a 1, neither do they pass automatically on a 20.

examples of checks
ie balance (roll to see if you stand after you fall), skill checks (ie open lock, disable device)

examples of saves and rolls
ie attack roll, saving throw

[jkm]

good to know. i go back through my combat log on resisted critical hits and i've yet to see a 1 confirm, but that may just be because i was missing on a 1 regardless.

[Roguewiz]

The power critical feat is pretty pointless imo. You can crit and roll a 1 on the confirm and still do full crit damage. A roll of one is not an auto-fail for a confirm critical roll.

Power Critical adds +4 to confirm. That 1, is now a 5, now add in the modifiers. You are closer to actually succeeding on the crit.