Dungeons & Dragons
Dice probability
Type dice notation and see the whole distribution - the average, the
spread, and your chance to hit a number. Same notation as the
dice roller: 2d6+3,
4d6kh3 (keep highest 3), 2d20kh1 (advantage). Runs in your browser.
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How it works
Dice probability shows the full distribution behind any dice expression, not just an average. Type notation like 2d6+3 or 4d6kh3 and you get every possible total, how likely each one is, the mean, the spread, and your chance to meet or beat a target number.
It answers questions a single roll cannot: how swingy is 1d12 versus 2d6 for the same average, or how much keep-highest shifts your expected result. The math is exact, computed from the full set of outcomes rather than simulated.
Example. Enter 4d6kh3, the standard ability-score roll. You will see the distribution peak around 12 to 13, an average near 12.24, and the odds of rolling 15 or higher on a single score.
FAQ
How is this different from the dice roller?
The roller gives you one random result. This calculator gives you the probabilities behind every possible result, so you can compare dice and plan around the odds. Use the dice roller when you just want to roll.
Does it support advantage and keep/drop?
Yes. Use kh and kl suffixes, for example 2d20kh1 for advantage or 4d6kh3 to keep the highest three of four dice.
How is 'chance to beat a number' calculated?
It sums the probability of every outcome at or above your target, giving the exact percentage chance to meet or exceed that number.
Are the probabilities simulated or exact?
Exact. The calculator enumerates the full outcome distribution of your expression rather than rolling a large sample, so the percentages are the true mathematical odds, not an approximation that shifts between runs.