Power Attack Stats

[The Souljourner]

So I was talking in another thread about how I didn't like the new power attack rules, because I felt they made it too much of a no brainer for two handed weapon guys. Someone challenged that assumption, and I decided I had to do some math....

Looking at the numbers, power attack actually gets worse the more damage you do. It makes sense.... if you do 1000 damage per hit, losing 5% chance to hit in order to get 2 more damage is just not worth it.

So what are the exact stats?

It looks as though, depending upon your base damage, there's always a number you should be shooting to hit on. The less damage you do, the higher that number is (and the more you'll use power attack).

This assumes a two handed weapon, btw.

If you do 10 damage normally, you want to power attack enough so you hit on a 15+

If you do 15 damage normally, you want to power attack enough so you hit on a 13+

If you do 20 damage normally, you want to power attack enough so you hit on 11+

And obviously if you already hit on that number or can't hit on that number, then don't power attack.

Interesting... I guess it's not as useful as I thought.

-The Souljourner

 

[Darklone]

Take DR that you can't overcome otherwise into account and it's pretty nice

You can include this consideration in your "normal" damage output... but it's at least some reason to take the feat.

 

[The Souljourner]

Also, you're only doing a point or two of extra damage on average... it's just a lot more spectacular when you do hit

I guess it's fine... I just wish they hadn't removed the ability to use it with light weapons.

-The Souljourner

 

[Spatzimaus]

This assumes a two handed weapon, btw.

If you do 10 damage normally, you want to power attack enough so you hit on a 16+

If you do 15 damage normally, you want to power attack enough so you hit on a 13+

If you do 20 damage normally, you want to power attack enough so you hit on 11+

Almost correct. If you do 10 damage normally, you do not gain any benefit from PA if it required a 16 or higher to hit. However, that's not the same as Power Attacking until it hits on a 16+. For example, if I do 10 damage and only need a 6+ to hit, I only want to Power Attack for 5, because I'd now do 20 damage (which, as you noted, has its break-even point at 11+). I'd be at the equilibrium point for my new damage.

The rule of thumb we used in 3E was this:

A = your average damage, adding the percentages for crits, STR modifiers, and so on. Most people can keep track of this number pretty easily, or estimate it.
B = 20 times your chance of hitting. This equals 21 minus the number you need to roll, so if you need a 16+, it's a 5.

A*(B/20) is your average damage per hit. Since Power Attack holds A+B constant (by trading one for the other), the maximum damage would be where A=B.

If A>B, Power Attack does you no good. Your average damage would just go down. You'd actually prefer to trade the other way, but there are no ways to do that. Attack bonuses are better than damage bonuses when figuring average damage.
If A<B, Power Attack until the two are equal. That'd take (B-A)/2 points.

In 3.5E with a 2-handed weapon, you just have to replace A with (A/2) before starting this math, since PA would limit (A/2)+B. That leads to the numbers you figured out: an A of 10 balances with a B of 5, so you'd need a 16+ to hit before Power Attack was worthwhile. A of 20 balances B of 10. If, as I pointed out earlier, A was 10 and B was 15 (hit on 6+), you'd PA for (B-(A/2))/2 = 5.

There are a couple exceptions to this:
> If you only need to hit, and damage is irrelevant, then of course Power Attack is pointless.
> If your attack bonus is so far above the AC that you could have hit on negative numbers, Power Attack until it requires a 2 to hit.
> If your attack bonus is so bad that you can only hit on a 20, feel free to Power Attack all you want, since you'll still hit on a 20. In fact, if you could have hit on a 19, it's still beneficial to do this if you can double your average damage per hit.
> If you're trying to brute-force through DR, subtract the DR soak from A.

 

[Darklone]

I'm with Wulf Ratbane here:

Always all Power Attack!

 

[The Souljourner]

Yeah, I went back to my numbers and realized I did the math wrong with a 30% chance to hit... that's 15+ not 16+.

-THe equation I came up with was this:

200*(%tohit) = 5*Dmg + 10

(I just multiplied everything by 100 to get non-decimal numbers, since they're a pain to do in your head)

So use this to figure out what you should be power attacking for...

10 damage is 60/200 = .30 or 30% chance to hit, which is 15+, so always power attack until you hit 15+

-The Souljourner

 

[Seule]

Try looking here: http://24.25.217.183/ddcalc.php
It's a complete calculator of how much you should power attack under all circumstances. I don't know the person who maintains it, but I like the results.

--Seule

 

[The Souljourner]

Using some elementary mathematics, we can reduce my equation to this:

(Damage + 2)/40 = % to hit.

Which means that if you normally do 38 or more damage, power attack is useless unless you could theoretically hit on a 1 or less.

Ahh math. Gotta love it.

-The Souljourner

 

[Spatzimaus]

10 damage is 60/200 = .30 or 30% chance to hit, which is 15+, so always power attack until you hit 15+

But that's not quite right either, as I was trying to point out.

Let's take the example I gave. You do 10 damage per hit, and you're in a situation where you need a 6+ to hit (75%). That's an average of 7.5 damage per attack.

My formula says, Power Attack for 5. 20 damage per hit, needing a 11+ to hit (50%) gives an average of 10.0 damage per attack.

Your formula says Power Attack for 9 (to go from 6+ to 15+). 28 damage per hit, needing a 15+ to hit (30%), gives an average of 8.4 damage per attack.

You can't say "always Power Attack to 15+" because if you started off far enough away from that goal, the extra damage you'd gain along the way would change where the balance point ends up. So, the break-even point depends on the initial chance, which your equation is missing; your equation holds if you were already fairly close to the break-even point.

 

[A'koss]

Originally posted by Seule:

Try looking here: http://24.25.217.183/ddcalc.php
It's a complete calculator of how much you should power attack under all circumstances. I don't know the person who maintains it, but I like the results.

Wow. Very cool... consider it bookmarked.


A'koss.