My barbarian is going to receive the Great Weapon Master feat. Looking over it, I have a question about the -5 to hit mentioned in the feat.
The second benefit of the Great Weapon Master feat (PHB, pg. 167):
Before you make a melee attack with a heavy weapon that you are proficient with, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.
Currently, I have a greataxe with a +5 modifier to the attack roll (+3 Str mod and +2 proficiency bonus). My question regards the -5 to hit from the feat. Do I subtract it from the +5 of the attack roll with the axe, giving me +0 attack bonus overall? Or does my overall modifier on the attack roll become a -5?