Roll a d20
One twenty-sided die, with advantage and your modifier handled for you. No ads and no signup. Need the other six dice? The full dice roller takes any notation you throw at it.
1d20
Nothing saved yet. Set up a roll above and keep it for the rest of the campaign.
Every roll tonight lands here, newest first.
1–7 pick a die · Enter roll · A advantage · D disadvantage
Odds
Your chance of success, for every target
Subtract your modifier from the DC. That is the number you need on the die. Find it in the first column and read across.
A rogue with a +7 Stealth rolling against DC 15 needs an 8, so a little over half the time they are seen. With advantage that becomes 84%.
| You need | Normal | Advantage | Disadvantage | Advantage is worth |
|---|---|---|---|---|
| 2 or higher | 95% | 100% | 90% | +5% |
| 3 or higher | 90% | 99% | 81% | +9% |
| 4 or higher | 85% | 98% | 72% | +13% |
| 5 or higher | 80% | 96% | 64% | +16% |
| 6 or higher | 75% | 94% | 56% | +19% |
| 7 or higher | 70% | 91% | 49% | +21% |
| 8 or higher | 65% | 88% | 42% | +23% |
| 9 or higher | 60% | 84% | 36% | +24% |
| 10 or higher | 55% | 80% | 30% | +25% |
| 11 or higher | 50% | 75% | 25% | +25% |
| 12 or higher | 45% | 70% | 20% | +25% |
| 13 or higher | 40% | 64% | 16% | +24% |
| 14 or higher | 35% | 58% | 12% | +23% |
| 15 or higher | 30% | 51% | 9% | +21% |
| 16 or higher | 25% | 44% | 6% | +19% |
| 17 or higher | 20% | 36% | 4% | +16% |
| 18 or higher | 15% | 28% | 2% | +13% |
| 19 or higher | 10% | 19% | 1% | +9% |
| 20 or higher | 5% | 10% | 0% | +5% |
The last column is the part people get wrong. Advantage is not a flat bonus. It does the most work when the roll is a coin flip and almost nothing when you were always going to make it or never had a chance.
The three rolls
What the d20 is actually for
Attack rolls
Beat the target’s Armour Class and you hit. Add your ability modifier and your proficiency bonus if you are proficient with the weapon.
Ability checks
Climbing, persuading, picking a lock. The DM sets a Difficulty Class, usually 10 for something fiddly and 20 for something genuinely hard.
Saving throws
Resisting something happening to you. The DC comes from whatever is doing it, most often a spell save DC of 8 plus the caster’s modifier and proficiency.
Natural 20
What a 20 does depends on which book you use
2014 Player’s Handbook
A natural 20 is an automatic hit on an attack roll, and it lets you roll your damage dice twice. On a death saving throw it brings you back with one hit point. On an ability check or an ordinary saving throw it does nothing special, and a natural 1 does nothing special either. Most tables house-ruled around this.
2024 Player’s Handbook
A natural 20 is an automatic success on any d20 test, whether that is an attack, a check or a save, and a natural 1 is an automatic failure. The old house rule became the rule. If your group is mid-campaign on the 2014 books, this is the change most worth agreeing on out loud.
Questions
Questions
- How do you roll a d20 online?
- Press the d20 above. It rolls one twenty-sided die and shows the face value. Set a modifier and it adds it for you, and if you are rolling with advantage or disadvantage it rolls the second die and keeps the right one.
- What do you roll a d20 for in D&D?
- Three things: attack rolls, ability checks and saving throws. All three work the same way. Roll the die, add the relevant modifier, and compare the total against a target number. For an attack that target is the enemy Armour Class. For a check or a save it is a Difficulty Class the DM sets.
- What are the odds of rolling a 20 on a d20?
- 5%, or one roll in twenty. With advantage it is 9.75%, because you get two chances and only need one of them to land. Disadvantage drops it to 0.25%.
- Does a natural 20 always succeed?
- It depends which rules you play. Under the 2014 Player's Handbook a natural 20 is an automatic hit on an attack roll and a success on a death saving throw, and nothing special on an ability check or an ordinary saving throw. The 2024 rules changed it: a natural 20 is an automatic success on any d20 test, and a natural 1 is an automatic failure. Plenty of tables ran the 2024 version as a house rule long before it was official.
- How much does advantage actually help?
- Between nothing and 25 percentage points, depending on what you need. It is worth most when you need an 11, where it takes you from 50% to 75%. It is worth least at the extremes: if you need a 2 you were already going to succeed, and if you need a 20 advantage only takes you from 5% to 9.75%. The table above shows the swing for every target.
- Is this d20 roller actually random?
- It uses the browser's cryptographic random number generator, the same one used for security tokens, rather than a simple pseudo-random shuffle. Over a session you should see roughly five of each face per hundred rolls. Streaks that feel impossible are normal: in a hundred rolls, a run of three identical results is more likely than not.
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The natural 20 that saved the party is a story beat, not a number. Saga20 turns your recorded sessions into a campaign wiki, so the rolls your table still talks about are written down somewhere.