OneTool

Dice Probability Calculator

Probability distribution for NdS±M dice rolls.

Probability of

  • Query probability

    62.50%

  • Range

    5–20

  • Mean

    12.5

  • Combinations

    216

Outcome distribution

  • 5
    0.46%
  • 6
    1.39%
  • 7
    2.78%
  • 8
    4.63%
  • 9
    6.94%
  • 10
    9.72%
  • 11
    11.57%
  • 12
    12.50%
  • 13
    12.50%
  • 14
    11.57%
  • 15
    9.72%
  • 16
    6.94%
  • 17
    4.63%
  • 18
    2.78%
  • 19
    1.39%
  • 20
    0.46%

What is this tool?

Parses standard dice notation (NdS±M) for common die sizes — d4, d6, d8, d10, d12, d20, and d100 — and builds the full probability distribution of totals. Query the chance of rolling at least, exactly, or at most a target value. Useful for tabletop RPG math, board-game odds, or any system that uses fair dice. Not affiliated with any specific game or publisher.

How to use it

  1. Enter dice notation such as 3d6+2, 2d8, or d20.
  2. Choose at-least / exactly / at-most and a target total.
  3. Read the query probability, mean, range, and the full outcome chart.

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