Dice Probability Calculator
This dice probability calculator shows the exact odds of every total for any roll, from 2d6 to 4d6 drop lowest or a d20 with advantage. Enter the dice and a target number to see the chance of rolling exactly that, at least that or less, plus the average, range and a full distribution chart.
Enter dice and a target, then press Calculate.
Average and range of common rolls
| Roll | What it means | Min | Average | Max |
|---|---|---|---|---|
| 2d6 | Two six-sided dice | 2 | 7 | 12 |
| 3d6 | Three six-sided dice | 3 | 10.5 | 18 |
| 1d20+5 | Attack roll with a +5 bonus | 6 | 15.5 | 25 |
| 2d20kh1 | d20 with advantage | 1 | 13.83 | 20 |
| 2d20kl1 | d20 with disadvantage | 1 | 7.18 | 20 |
| 4d6dl1 | One ability score | 3 | 12.24 | 18 |
| 8d6 | Fireball | 8 | 28 | 48 |
| 2d8+4 | Two hits of 1d8+2 | 6 | 13 | 20 |
Supported notation
- NdX: roll N dice with X sides, e.g. 3d6. Leave out N to roll one die (d20).
- + / − M: add or subtract a number or more dice, e.g. 1d8+1d6+3.
- khN / klN: keep the highest or lowest N dice. 2d20kh1 is advantage, 2d20kl1 is disadvantage.
- dlN / dhN: drop the lowest or highest N dice. 4d6dl1 is the classic ability-score roll.
- d%: the same as d100.
How dice probability works
Counting outcomes: Every face of a fair die is equally likely, so the chance of a total is the number of ways to make it divided by all possible outcomes. Two d6s have 36 outcomes and six of them add to 7, so 7 comes up 6/36 = 16.67% of the time. The calculator does this counting exactly for any roll; nothing is simulated.
Why sums form a bell curve: One die is flat, but adding dice makes middle totals far more likely than extremes, because there are many more ways to make them. The more dice you add, the tighter the curve. See the full 2d6 and 3d6 probability tables.
Use "or higher" for DCs: In D&D you usually need to meet or beat a number, so the "this or higher" column is the one that matters. Enter 1d20+5 and target 15 to see your chance of hitting AC 15 with a +5 bonus. Want to roll the dice instead? Use the dice calculator.
Dice Probability Calculator FAQ
How do you calculate dice probability?
Count the outcomes that give the result you want and divide by the total number of outcomes. For two six-sided dice there are 36 outcomes, so a total of 7 (six ways) has a probability of 6/36, about 16.67%.
What is the most likely roll with 2d6?
7 is the most likely total with two six-sided dice, at 16.67%. The least likely totals are 2 and 12, at 2.78% each.
How likely am I to hit with a +5 attack bonus?
Against AC 15 you need 10 or higher on the d20, which is a 55% chance. Enter 1d20+5 with target 15 in the calculator to see the exact odds for any AC.
Can it calculate advantage and drop lowest?
Yes. Use 2d20kh1 for advantage, 2d20kl1 for disadvantage and 4d6dl1 for 4d6 drop lowest. The calculator works these out exactly by checking every possible roll.
Is this like AnyDice?
It answers the same kind of question, but you only type standard dice notation; there is no programming language to learn. For complex custom mechanics, AnyDice is more flexible.
Related
- Dice Calculator
- 2d6 and 3d6 Probability Tables
- Advantage and Disadvantage in 5e: How It Changes Your Odds
Other dice
- 3D Dice Roller
- Roll a d2
- Roll a d3
- Roll a d4
- Roll a d6
- Roll a d8
- Roll a d10
- Roll a d12
- Roll a d20
- Roll a d100
- Roll a d1000
About this roller
DnD Dice Roller (dnddiceroller.org) rolls every die with your browser's cryptographically secure random number generator, crypto.getRandomValues, and uses rejection sampling so every face is exactly equally likely. The 3D dice only animate a result that has already been decided this way; the physics never picks the number. Rolls happen on your device and are never sent to our server.
The site is built and maintained by Farooq Choudhary at Ozeito, which also publishes the DnD Dice Roller app for Android and iOS. Found a problem? Contact us.
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Contains content from the System Reference Document 5.1 and 5.2 by Wizards of the Coast LLC, used under the Creative Commons Attribution 4.0 International License.