Understanding the 2 Dice Roller
When you roll two standard six-sided dice, each die is independent and shows a number from 1 to 6 with equal probability. Because die A has 6 faces and die B has 6 faces, there are 6 × 6 = 36 equally likely ordered outcomes — from (1,1) up to (6,6). Every probability on this page is just the count of outcomes that satisfy your condition, divided by 36.
How the sum is distributed
The two dice can total anywhere from 2 (a pair of ones) to 12 (a pair of sixes). The totals are not equally likely, though: a 7 can be built six different ways, while a 2 or a 12 can each be built only one way. This gives the classic triangular ("tent") distribution that peaks at 7 and is perfectly symmetric around it.
| Sum | Ways to make it | Probability | Percent |
|---|---|---|---|
| 2 | 1 | 1/36 | 2.78% |
| 3 | 2 | 1/18 | 5.56% |
| 4 | 3 | 1/12 | 8.33% |
| 5 | 4 | 1/9 | 11.11% |
| 6 | 5 | 5/36 | 13.89% |
| 7 | 6 | 1/6 | 16.67% |
| 8 | 5 | 5/36 | 13.89% |
| 9 | 4 | 1/9 | 11.11% |
| 10 | 3 | 1/12 | 8.33% |
| 11 | 2 | 1/18 | 5.56% |
| 12 | 1 | 1/36 | 2.78% |
The 11 counts add up to 1 + 2 + 3 + 4 + 5 + 6 + 5 + 4 + 3 + 2 + 1 = 36, confirming every outcome is accounted for exactly once.
The formula
- Exact sum: P(sum = s) = ways(s) / 36, where ways(s) counts the (die A, die B) pairs that add to s. For s from 2 to 7 the count rises as 6 − |7 − s|; from 7 to 12 it falls by the same rule.
- At least / at most: P(sum ≥ s) and P(sum ≤ s) add up the individual ways across all qualifying totals, then divide by 36. For example P(sum ≥ 10) = (3 + 2 + 1)/36 = 6/36 = 1/6.
- Odds against: if f outcomes are favorable, the odds against are (36 − f) : f, reduced to lowest terms. A 7 has odds of 30 : 6 = 5 : 1 against.
Key reference points
- Most likely total: 7, at 6/36 ≈ 16.67%.
- Rarest totals: 2 and 12, each at 1/36 ≈ 2.78%.
- Expected value: the mean sum is 7 (each die averages 3.5, and 3.5 + 3.5 = 7).
- Doubles: six of the 36 outcomes are doubles (1-1 through 6-6), so any double is 6/36 = 1/6 ≈ 16.67%.
- Beating a 7: P(sum > 7) = P(sum < 7) = 15/36 ≈ 41.67% by symmetry, leaving 6/36 for exactly 7.