Advantage raises the average roll from 10.5 to 13.825, which is roughly like a +3 to +5 bonus for middling targets.
Dice notation
| You type | Meaning |
|---|---|
d20 | One 20-sided die |
3d6+2 | Three six-sided dice plus 2 |
1d8+1d6-1 | Mixed dice and a modifier |
4d6dl1 or 4d6kh3 | Roll four d6, drop the lowest (keep the highest three) |
2d20kh1 / 2d20kl1 | Advantage / disadvantage |
d% or d100 | Percentile die, 1 to 100 |
How the rolls and odds work
DiceKit draws each die from your browser's cryptographic random number generator (crypto.getRandomValues), using rejection sampling so no face is favoured. Nothing is sent anywhere. The odds are exact: plain dice are combined one at a time (a convolution of their distributions), and keep or drop rules are calculated by counting every possible combination. Only very large keep or drop pools are estimated by simulation, and the result says so.
Handy averages
| Dice | Average | Range |
|---|---|---|
| d6 | 3.5 | 1–6 |
| 2d6 | 7 | 2–12 |
| 3d6 | 10.5 | 3–18 |
| 4d6 drop lowest | 12.24 | 3–18 |
| d20 | 10.5 | 1–20 |
| d20 with advantage | 13.83 | 1–20 |
| d20 with disadvantage | 7.18 | 1–20 |
| 8d6 | 28 | 8–48 |
Frequently asked questions
How much is advantage worth?
About +3.3 on average, and up to +5 when you need around an 11.
What is the average roll with disadvantage?
7.175.
Do advantage and disadvantage stack?
In D&D 5e, no; if you have both, they cancel and you roll one d20.
Is DiceKit free?
Yes, with no sign-up or ads.
Is my roll history saved?
Yes, in this browser only, and you can clear it at any time.