For roll-under systems, a skill of 45% succeeds on a roll of 45 or less, a 45% chance.
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 do you roll a d100 with two d10s?
One die is the tens and the other the units; 00 and 0 together usually read as 100.
Is d% the same as d100?
Yes.
What is the average of a d100?
50.5.
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.