Can someone explain the Great Weapon Fighting style feat?

Does the effect apply to all dice or just one?

When you roll damage for an attack you make with a Melee weapon that you are holding with two hands, you can treat any 1 or 2 on a damage die as a 3. The weapon must have the Two-Handed or Versatile property to gain this benefit.

It affects all of your dice on the attack. So if you attack with a Greatsword, the affect applies to both dice. It also applies to anything that might add damage to the attack, such as Sneak Attack, Hex, or the extra damage from a magic weapon like a Flame Tongue Greataxe.

I will point out, that this damage bonus sounds better that it actually is. The average die roll for a d6 will only change from 3.5 to 4. The damage increase gets even smaller as the size of the die goes up. On a d12, it is only 0.25 more average damage per die.

Thanks!

I am not entirely convinced that's correct. The Feat affects the weapon damage rolls, but i'm not sure it also affects additional damage from other sources. Will need to research it more.

Quote from HarmAssassin >>

I am not entirely convinced that's correct. The Feat affects the weapon damage rolls, but i'm not sure it also affects additional damage from other sources. Will need to research it more.

It was clarified in Sage Advice here that it does not apply to dice from add-on damage effects like Hex.

That said, in practice a lot of DMs (including me) would probably allow it to apply to things like that, because otherwise it's a pretty garbage feat.

Garbage might not be the right word. It takes you minimum damage with normal great sword from 2+mods to 6+mods. With extra attack that stacks quickly with some decent damage each hit. Also the goes crazy at low levels. If you have a +3 in strength then you deal minimum of 9 damage per hit which is a definite one shot of a goblin minion. It removes the chance of not on taping low hit point monsters. If you multiclass to Ranger or warlock and grab hex/hunters mark that adds another 3 on there. Seem at least ok to me.