D20 Die Roller
Roll a twenty-sided die online with advantage, disadvantage, and modifiers — built for D&D 5e, Pathfinder, and any RPG that runs on the d20.
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Common D20 Roll Types
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About the D20
The twenty-sided die (D20) is the most iconic die in tabletop role-playing games, especially Dungeons & Dragons. It is used for determining the success or failure of most actions in the game.
Common D20 Uses:
- Attack Rolls: To determine if attacks hit their targets
- Saving Throws: To resist spells, traps, poisons, and other dangers
- Ability Checks: To determine success when using skills or abilities
- Initiative: To determine turn order in combat
Understanding Advantage & Disadvantage
In D&D 5th Edition and similar systems, advantage and disadvantage are mechanics that represent favorable or unfavorable circumstances affecting a roll.
| Mechanic | How It Works | When It's Used |
|---|---|---|
| Advantage | Roll two D20s and take the higher result | When circumstances favor you (attacking a prone enemy, having help, etc.) |
| Disadvantage | Roll two D20s and take the lower result | When circumstances hinder you (attacking while prone, in difficult terrain, etc.) |
When you have both advantage and disadvantage, they cancel each other out, regardless of how many sources of each you have.
D20 Probability: Know Your Odds
Every face of a fair d20 has an equal 1-in-20 (5%) chance, so the chance of meeting or beating a target number is easy to compute: there are 21 − N winning faces out of 20, where N is the number you need. Advantage and disadvantage change those odds dramatically — with advantage you succeed unless both dice fail, and with disadvantage you need both dice to succeed. The table below shows the exact chance of rolling each target number or higher before modifiers:
| Roll Needed | Normal Roll | With Advantage | With Disadvantage |
|---|---|---|---|
| 5+ | 80% | 96% | 64% |
| 8+ | 65% | 87.75% | 42.25% |
| 10+ | 55% | 79.75% | 30.25% |
| 11+ | 50% | 75% | 25% |
| 12+ | 45% | 69.75% | 20.25% |
| 15+ | 30% | 51% | 9% |
| 18+ | 15% | 27.75% | 2.25% |
| Natural 20 | 5% | 9.75% | 0.25% |
A normal d20 roll averages 10.5. Advantage lifts that average to 13.82 and disadvantage drops it to 7.18 — so advantage is worth about +3.3 on average. Its real value depends on what you need to roll, though: it peaks at the equivalent of a +5 bonus when you need an 11 (50% → 75%), and matters least on rolls you would almost always make or almost always miss anyway. For a deeper dive into the math, see our guide to dice probability mathematics.
When Do You Roll With Advantage or Disadvantage?
Common Sources of Advantage (5e)
- Attacking a prone creature from within 5 feet
- Attacking a creature that can't see you (hidden or invisible attacker)
- Attacking a restrained, stunned, or paralyzed target
- An ally uses the Help action on your attack or check
- A Barbarian using Reckless Attack (Strength melee attacks)
- Spending Inspiration on an attack, save, or check
Common Sources of Disadvantage (5e)
- Attacking at long range with a ranged weapon
- Making a ranged attack while a hostile creature is within 5 feet
- Attacking while you are prone
- Attacking a target you can't see
- Being poisoned (attack rolls and ability checks)
- Attacking a prone creature from more than 5 feet away
Remember: sources of advantage and disadvantage never stack. If you have at least one of each, they cancel completely and you make a single normal roll — even if you have three reasons for advantage and only one for disadvantage.
D20 Roller FAQ
What are the odds of rolling a natural 20?
On a single d20, every face has a 1-in-20 chance, so a natural 20 comes up 5% of the time. Rolling with advantage raises the chance of at least one natural 20 to 9.75%.
How much is advantage worth?
Advantage raises the average d20 result from 10.5 to about 13.82 — roughly a +3.3 bonus on average, peaking at the equivalent of +5 when you need an 11.
Do multiple sources of advantage or disadvantage stack?
No. You never roll more than two d20s: any number of advantage sources still means rolling twice and taking the higher. Having both advantage and disadvantage — from any number of sources — cancels out to a single normal roll.
Does a natural 20 always succeed?
It depends on the roll and the edition. In the 2014 D&D 5e rules, a natural 20 automatically hits on attack rolls (and scores a critical hit) but is not an automatic success on ability checks or saving throws. In the 2024 rules, a natural 20 automatically succeeds on any D20 Test.