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Polyhedral dice — modifiers, advantage & disadvantage
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How D&D 5e dice work
Dungeons & Dragons 5th Edition uses the standard polyhedral set, from the d4 to the d20. The d20 decides whether you succeed; the smaller dice decide how much damage or healing happens once you do.
The dice
| Die | Typical uses |
|---|---|
| d4 | Dagger damage, Bless and Guidance, healing potions (2d4 + 2) |
| d6 | Shortsword and shortbow damage, Fireball (8d6), Sneak Attack |
| d8 | Longsword and rapier damage, Cure Wounds |
| d10 | Heavy crossbow damage, Fire Bolt, half of a percentile roll |
| d12 | Greataxe damage, a barbarian's Hit Dice |
| d20 | Attack rolls, ability checks and saving throws |
| d100 | Percentile tables: wild magic surges, random loot |
Damage is written as a number of dice plus a modifier: 2d6 + 3 means roll two d6s and add 3. A d100 is two d10s, one for the tens and one for the ones.
Checks, advantage and crits
Attack rolls, ability checks and saving throws are all a d20 plus a modifier, against a target number such as an Armor Class or a Difficulty Class. Meet or beat it and you succeed.
With advantage, roll two d20s and keep the higher. With disadvantage, keep the lower. Several sources of advantage still mean only two dice, and having both advantage and disadvantage cancels out to a single die.
On an attack roll, a natural 20 always hits and is a critical hit: roll the damage dice twice. A natural 1 always misses.
What advantage is worth
Advantage raises the average d20 roll from 10.5 to 13.8, and disadvantage lowers it to 7.2. It matters most when you need a 10 or 11.
| Need on the die | Normal | Advantage | Disadvantage |
|---|---|---|---|
| 5 or higher | 80% | 96% | 64% |
| 10 or higher | 55% | 79.8% | 30.3% |
| 15 or higher | 30% | 51% | 9% |
| 20 or higher | 5% | 9.8% | 0.3% |