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Dice probability uses combinatorics to calculate the exact likelihood of rolling specific sums or outcomes with one or more dice. The distribution of sums follows a discrete probability distribution that becomes approximately bell-shaped (normal) as more dice are added — an illustration of the Central Limit Theorem.

公式

P(sum = T) = ways / total outcomes
P
T) = ways / total outcomes — T) = ways / total outcomes
T
ways / total outcomes — ways / total outcomes

ステップバイステップガイド

  1. 1Total outcomes for d dice with s sides: sᵈ
  2. 2Count ways to roll exactly target sum T: dynamic programming (convolution of dice distributions)
  3. 3P(sum = T) = ways / total outcomes
  4. 4Expected sum for d dice with s sides: d × (s+1)/2
  5. 5Variance: d × (s²−1)/12

解いた例

入力
2d6, sum = 7
結果
6/36 = 16.7%
Most common sum on 2d6; 6 ways out of 36
入力
2d6, sum = 12
結果
1/36 = 2.8%
Only one way: (6,6)
入力
3d6, sum = 10
結果
27/216 = 12.5%
Peak of 3d6 distribution

よくある質問

What is Dice Probability?

Dice probability uses combinatorics to calculate the exact likelihood of rolling specific sums or outcomes with one or more dice. The distribution of sums follows a discrete probability distribution that becomes approximately bell-shaped (normal) as more dice are added — an illustration of the Central Limit Theorem

How accurate is the Dice Probability calculator?

The calculator uses the standard published formula for dice probability. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Dice Probability calculator use?

This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Dice Probability calculator use?

The core formula is: P(sum = T) = ways / total outcomes. Each step in the calculation is shown so you can verify the result manually.

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