Resistance, Vulnerability and Immunity, Half, Double or Nothing
The Fighter's sword hits the Ghost for 9. The GM says "it takes 4." The player frowns. The Cleric's mace hits a Skeleton for 7, and the GM says "14." Damage types decide this, and SRD 5.2.1 gives them three short rules and an order. Here they are, quoted, with the numbers worked out.
Every hit has a type
Every source of damage names a type: Slashing, Piercing, Bludgeoning, Fire, Cold, Necrotic, Force and the rest. Most of the time the type changes nothing. The SRD says why it still matters:
Damage types are defined in "Rules Glossary" and have no rules of their own, but other rules, such as Resistance, rely on damage types.
So read the type on every attack, every spell and every stat block. A Warhammer deals Bludgeoning. Fire Bolt deals Fire. Ray of Frost deals Cold.
Resistance halves, Vulnerability doubles
If you have Resistance to a damage type, damage of that type is halved against you (round down). If you have Vulnerability to a damage type, damage of that type is doubled against you.
Round down matters. A hit for 7 against Resistance does 3, not 3.5 and not 4. A hit for 1 does 0.
Immunity stops it
Immunity to a damage type means you don't take damage of that type, and Immunity to a condition means you aren't affected by it.
Stat blocks list both under one heading. The Skeleton's reads "Immunities Poison; Exhaustion, Poisoned": damage types before the semicolon, conditions after.
They don't stack
Multiple instances of Resistance or Vulnerability that affect the same damage type count as only one instance.
A creature with Resistance to Necrotic and Resistance to all damage takes half from Necrotic, not a quarter. Two sources of Resistance are one Resistance.
The order
Modifiers to damage are applied in the following order: adjustments such as bonuses, penalties, or multipliers are applied first; Resistance is applied second; and Vulnerability is applied third.
The SRD's own example: a creature with Resistance to all damage and Vulnerability to Fire stands in an aura that reduces all damage by 5. It takes 28 Fire damage.
| Step | Rule | Damage |
|---|---|---|
| Roll | Fire damage | 28 |
| 1 | Aura: minus 5 | 23 |
| 2 | Resistance: half, round down | 11 |
| 3 | Vulnerability: double | 22 |
Resistance and Vulnerability to the same type don't cancel. Both apply, in order, and the round-down in step 2 costs a point.
A Skeleton and a Warhammer
The SRD Skeleton: AC 14, 13 Hit Points, "Vulnerabilities Bludgeoning". Take a Fighter with Strength 16 (+3).
- Longsword (1d8 + 3 Slashing): 4 to 11 damage. It never drops the Skeleton in one hit. Two hits drop it 76.6% of the time.
- Warhammer (1d8 + 3 Bludgeoning, doubled): 8 to 22, average 15. One hit drops it 62.5% of the time, on any 4 or better on the d8.
Same Fighter, same Strength, same d8. Pick up the hammer.
A Ghost and a sword
The SRD Ghost has 45 Hit Points and a long list: "Resistances Acid, Bludgeoning, Cold, Fire, Lightning, Piercing, Slashing, Thunder" and "Immunities Necrotic, Poison".
The Fighter's Longsword averages 7.5 a hit. Halved and rounded down, the d8 gives 2, 2, 3, 3, 4, 4, 5, 5: an average of 3.5. The fight lasts more than twice as long. Fire Bolt and Ray of Frost are halved too. Necrotic does nothing at all.
What's left off the list: Force, Psychic, Radiant. Magic Missile (Force) and Sacred Flame (Radiant) hit a Ghost at full strength. Read the list for what's missing.
A Magma Mephit: nothing, then double
The SRD Magma Mephit: 18 Hit Points, "Vulnerabilities Cold", "Immunities Fire, Poison".
- Fire Bolt (1d10 Fire): 0 damage, every time.
- Ray of Frost (1d8 Cold, doubled): 2 to 16, average 9. It drops the Mephit in two hits 56.25% of the time, and takes 2.6 hits on average. Undoubled, the same cantrip would need 4.5.
A Wizard who knows both cantrips gets to choose. A Wizard who knows only Fire Bolt watches.
Resistance on your side: Rage
Barbarians carry Resistance into every fight. While raging:
Damage Resistance. You have Resistance to Bludgeoning, Piercing, and Slashing damage.
A level 1 Barbarian has 12 + Constitution modifier Hit Points: 14 with Con +2. The SRD Ogre's Greatclub hits for 2d8 + 4 Bludgeoning, average 13.
| One hit drops you | Average hits to drop | |
|---|---|---|
| Not raging | 43.75% | 1.6 |
| Raging | 0% | 2.7 |
Raging, the Greatclub does 3 to 10. The Ogre can't drop the Barbarian with one swing, and needs three swings 63% of the time.
Temporary Hit Points
Temporary Hit Points aren't Resistance, but they do the same job: they stand between a hit and your real Hit Points.
If you have Temporary Hit Points and take damage, those points are lost first, and any leftover damage carries over to your Hit Points.
The SRD's example: 5 Temporary Hit Points and 7 damage leaves you down 2 Hit Points.
Three rules catch tables out.
Temporary Hit Points can't be added together. If you have Temporary Hit Points and receive more of them, you decide whether to keep the ones you have or to gain the new ones.
So 10 and then 12 is 12, not 22.
Temporary Hit Points can't be added to your Hit Points, healing can't restore them, and receiving Temporary Hit Points doesn't count as healing.
If you have 0 Hit Points, receiving Temporary Hit Points doesn't restore you to consciousness. Only true healing can save you.
They last "until they're depleted or you finish a Long Rest."
A Wizard behind False Life
False Life is a level 1 spell for Sorcerers and Wizards:
You gain 2d4 + 4 Temporary Hit Points.
That's 6 to 12, average 9. A level 1 Wizard with Con +1 has 7 Hit Points. A Goblin Warrior's Scimitar hits for 1d6 + 2.
| One hit drops you | Down within two hits | Average hits to drop | |
|---|---|---|---|
| No False Life | 33.3% | 97.2% | 1.7 |
| False Life | 0% | 6.1% | 3.4 |
One spell slot, cast before the door opens, roughly doubles the hits it takes to put the Wizard down.
At the table
- Say the type. "9 Slashing" not "9". The GM needs it, and the player who says it every time never gets the frown.
- Round down once. Halve the total after every bonus, not each die.
- Read the gaps. The list of what a monster resists tells you what it doesn't.
- Temporary Hit Points go in their own box. The character sheet has one. Don't add them to the real ones.
The Book of Dice covers the d8 and the d10 behind these numbers in Part I, The Object.
This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License.
