[RPG] Does a rogue’s Uncanny Dodge halve each type of damage individually or the total


The rogue has the Uncanny Dodge class feature, which says this (PHB, pg. 96):

Starting at 5th level, when an attacker that you can see hits you with an attack, you can use your reaction to halve the attack's damage against you.

As pointed out in the answers to this question, if an attack has multiple damage types, you half all of it. So consider the Spiked Bone Club attack of the Grimlock (MM, pg. 175):

Spiked Bone Club. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) bludgeoning damage plus 2 (1d4) piercing damage.

The Grimlock attacks the level 5 rogue and hits, and the DM rolls damage. The first d4 gives a 2, giving a total of 5 bludgeoning damage, and the other d4 gives a 3, giving a total of 3 piercing damage. The grand total is 8 damage.

Given that damage is rounded down when halved, do we:

  • round each individual total down, which in this example is (5 / 2) + (3 / 2) = 2 + 1 = 3?
  • round down the grand total, which in this example is (5 + 3) / 2 = 8 / 2 = 4?

Best Answer

Uncanny Dodge halves the individual types

The wording doesn't use reference to damage types or to the concept of resistance, so you're not reducing the damage because you're resistant to it, but rather because you're quick and agile and can dodge the brunt of it.

The Jeremy Crawford Tweet that Grosscol's answer mentioned uses language that lumps the damage into "one big damage roll," which is what this feature affects. All of this would suggest that you could halve the total and be done with it, however:

Resistances/vulnerabilities are calculated last

Resistance and then vulnerability are applied after all other modifiers to damage. - (PHB 197)

This means that you have to apply Uncanny Dodge before you apply any resistances or vulnerabilities. This is impossible without abandoning rounding in any cases involving odd numbers. In order to be able to apply Uncanny Dodge before an effect that alters individual damage types, you must apply it to those individual types too!

For example:

An Ice Devil (MM 75) hits Bobby with it's Claws, dealing 9 slashing damage and 11 cold damage.

Bobby, a level 10 rogue, is wearing the Boots of the Winterlands (DMG 156) giving him resistance to cold. He also uses his Uncanny Dodge ability.

Resistance is calculated last, so we must calculate Uncanny Dodge first. If we halve the total (20) for 10 damage, what damage is halved by cold resistance? If instead we halve both individually (4 slashing, 5 cold) then we have a cold type damage value (5) to halve at the end using resistance.