[RPG] Adding Precision Strike to an attack with advantage

advantage-and-disadvantagednd-5e

I want to make sure I have the ruling on this correct.

-Precision Attack- When you make a weapon attack roll against a creature, you can expend one superiority die to add it to the roll.
You can use this maneuver before or after making the attack roll, but
before any effects of the attack are applied.

This means that if I'm attacking with advantage, I can roll both d20's, and the decide which of those (obvious the higher) to add my d8 to, just to further cinch the hit if I'm against an uber-evasive/heavily-armored opponent.

Best Answer

Just to break it down, here's how attack rolls work:

When you make an attack, your attack roll determines whether the attack hits or misses. To make an attack roll, roll a d20 and add the appropriate modifiers.

And here's how advantage changes that:

Sometimes a special ability or spell tells you that you have advantage or disadvantage on an ability check, a saving throw, or an attack roll. When that happens, you roll a second d20 when you make the roll. Use the higher of the two rolls if you have advantage, and use the lower roll if you have disadvantage.

Putting these together, we get this: When you make an attack, your attack roll determines whether the attack hits or misses. To make an attack roll, roll two d20s and use the higher roll, then add the appropriate modifiers.

So, even if you chose to roll your d8 before you made the roll, it would still get added to the higher roll. Of course, as you say, you can decide to use the d8 after you've already made the roll, which is to say, after you've rolled 2 d20s, used the highest, and added the appropriate modifiers to it.