How advantage and disadvantage work
In the fifth edition rules, advantage means you roll two d20s and use the higher one; disadvantage means you use the lower one. They never stack: two sources of advantage still mean two dice, and if you have both advantage and disadvantage they cancel out and you roll one die. Your modifier is added once, to the die you keep.
Odds with advantage and disadvantage
The chance of hitting a target number on the die, before modifiers:
| Need on the die | Normal | Advantage | Disadvantage |
|---|---|---|---|
| 2+ | 95% | 99.75% | 90.25% |
| 3+ | 90% | 99% | 81% |
| 4+ | 85% | 97.75% | 72.25% |
| 5+ | 80% | 96% | 64% |
| 6+ | 75% | 93.75% | 56.25% |
| 7+ | 70% | 91% | 49% |
| 8+ | 65% | 87.75% | 42.25% |
| 9+ | 60% | 84% | 36% |
| 10+ | 55% | 79.75% | 30.25% |
| 11+ | 50% | 75% | 25% |
| 12+ | 45% | 69.75% | 20.25% |
| 13+ | 40% | 64% | 16% |
| 14+ | 35% | 57.75% | 12.25% |
| 15+ | 30% | 51% | 9% |
| 16+ | 25% | 43.75% | 6.25% |
| 17+ | 20% | 36% | 4% |
| 18+ | 15% | 27.75% | 2.25% |
| 19+ | 10% | 19% | 1% |
| 20+ | 5% | 9.75% | 0.25% |
On average advantage turns a 10.5 into about 13.8 and disadvantage into about 7.2. Near the middle of the table that is worth roughly +5 or −5, which is where the ±5 to passive scores comes from.
Common reasons to roll with advantage
- Attacking a target you cannot be seen by, or one that is restrained, blinded or knocked prone next to you.
- Help from an ally with the Help action.
- Class features such as a barbarian's Reckless Attack.
- Inspiration from the DM, under many tables' rules.
Disadvantage comes from things like attacking at long range, being poisoned, frightened or prone, or attacking a target you cannot see.
More dice tools
Need a plain d20? Use the d20 roller. For damage dice and anything else, the D&D dice roller reads notation such as 1d20+7 adv or 2d8+4.
Last reviewed October 26, 2026. Odds in the tables are worked out exactly, not simulated.