Rolling a d20
The table opens with one twenty-sided die. Press Roll, the Space bar or the table itself, and the die flies in, bounces and settles on its result; click again to skip the animation. The total sits on the table and under it, and every roll goes into History with its time, so you can scroll back to a check you made three turns ago.
A 20 on the die is tagged Natural 20! and a 1 Natural 1. In the fifth edition rules (System Reference Document 5.2.1), a natural 20 on an attack roll hits whatever the target’s Armor Class and is a Critical Hit, and a natural 1 misses whatever your modifiers. Ability checks and saving throws don’t have that rule in the core game, though many tables add it.
Advantage and disadvantage
When a roll has advantage, the rules say to roll a second d20 and use the higher of the two; with disadvantage, the lower. Tap the Advantage or Disadvantage quick pick and both dice go on the table. How much that matters depends on the number you need:
| You need | Plain d20 | Advantage | Disadvantage |
|---|---|---|---|
| 10 or more | 55% | 79.75% | 30.25% |
| 15 or more | 30% | 51% | 9% |
| 20 (natural 20) | 5% | 9.75% | 0.25% |
Advantage helps most when you need around 11: it adds about 25 percentage points there, and only 4.75 at the extremes. The Odds tab shows the exact chance of every result for whatever is on the table, so you can check any other target.
Adding a bonus
Type 1d20+7 for a skill check with a +7 bonus, or use the Modifier stepper. The result line then shows the die and the bonus separately, such as 14 + 7 = 21, which is what a game master usually wants to hear.
Sources
The natural 20, natural 1 and advantage rules are from the System Reference Document 5.2.1 (Wizards of the Coast, CC BY 4.0), “D20 Tests”. The probabilities are worked out exactly from the 20 or 400 equally likely outcomes.
This page always opens with 1d20 on the table: dice you change here aren’t saved, while your colors, sound and roll history are. To start from your own dice every time, use the dice roller.