D&D 5E When to turn on Great Weapon Master

[shoak1]

The mathematical break-even point for turning on Great Weapon Master is whenever you need an 8 or less to hit a creature. Turn GWM on when you need this number or less, and turn it off otherwise. Three caveats:

1) This formula assumes you do 15 avg damage per attack (not counting the GWM +10). For every 2 points less damage you do on average, add 1 to the Target # - for every 2 points more damage, subtract 1 from the Target #.

2) If you are likely to kill a creature w/a hit without using the +10, turn GWM off.

3) Obviously there are certain in-game scenarios that trump the math in determining when to use this feat (such as having only 2 rounds to kill a monster and you should focus more on reliable damage than on max average damage per round).

A PC will not always know what AC a creature has, but knowing this target number at least gives a player a better understanding of when to use it.

THE MATH BEHIND THE TARGET #:
A player will roll an 8 or higher 65% of the time. If he turns GWM on, he will only hit 40% of the time. At 15 damage, GWM OFF scores 65% x 15 = 9.75 dmg, and GWM ON scores 10 dmg.

As the baseline chance to hit goes up, GWM gets better - for instance at 75% chance to hit, the results come in at 75% x 15 dmg = 11.25 dmg for GWM OFF. GWM ON scores 50% x 25 = 12.5.

Not unexpectedly, as the baseline chance to hit goes down, so does GWM's effectiveness.

As for damage variations, each +2 of damage "costs" the GWM ON hero 25% (the increased chance of a miss) x 2 = 0.5 damage. Conversely every pip extra chance of GWM striking gives 5% x 10 = 0.5 extra damage. So every 2 damage affects the target number by 1.

 

[Zardnaar]

There is no magic number depends on the situation I have seen it used against AC 20.

 

[shoak1]

There is no magic number depends on the situation I have seen it used against AC 20.

Huh? How does anecdotal evidence change math? Of course GWM *COULD* be used successfully vs anyone. But that doesn't mean it is a good idea to do so. You *COULD* drive home without your seat belt on and be fine - but it doesn't mean you *SHOULD*. Math helps us figure out if we SHOULD do something.

And calling the break-even number for GWM a "magic number" is dismissive of the mathematics behind it - and not a very defensible position given that the computer/phone you are using right now is based on mathematics as well.

 

[jgsugden]

Your math is focused on average damage. That is only a small part of the equation.

How many hps does the enemy have? Are there 'on hit' benefits that come with hitting such as knocking prone with Fellhanded? Is there an offesting benefit on a miss (damage on a miss)? How much damage can an enemy do if I do not take it down this round before it can go?

Understanding the math gives you a good tool, but is only one of many tools that you need to consider when evaluating options like GWM.

 

[CapnZapp]

I realize you're trying to offer a simple guideline to using GWM, but really all you're doing is illustrating why it is such a headache.

 

[Zardnaar]

Here are my rough guidlines.

Use it Most of the Time.
Zombies, Ogres

Rarely use it without support.
Chainmail+shields or better.

 

[Helldritch]

Here are my rough guidlines.

Use it Most of the Time.
Zombies, Ogres

Rarely use it without support.
Chainmail+shields or better.

That is exactly what my players are doing. The best guideline on that feat so far.
I would add:"Use it if you have advantage or some magic that benefits to hit rolls like bless".

 

[One_Shots]

http://www.enworld.org/forum/showth...-overpowered&p=6914942&viewfull=1#post6914942

 

[jaelis]

Accounting for the impact of advantage and disadvantage seems important.

 

[Blue]

First things first - I like this approach. Straightforward, easy to implement at the table.

How would you add in advantage, considering all of the barbarians with GWM? That both changes the chance to hit variably but also close to doubles chance for a crit. Is it possible to condense that to a nice rule-of-thumb like you have for the rest?

3) It assumes you never fell a creature and get the bonus attack. If you are likely to kill a creature w/a hit, have another creature you can attack, AND the bonus action slot is available, almost always turn GWM on.

I'd like to modify this to "if you are likely to kill a creature with a hit AND NOT WITHOUT THE +10...". First if you'll kill without the +10 the extra damage is just wasted overkill for a lesser chance to hit. And second you don't need to be using the feat (or even wielding a heavy weapon, as long as it's a melee weapon) to get the bonus attack.