Initiative order probability calculator

Calculate probability each participant acts first and expected finishing position by participant with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use probability each participant acts first and expected finishing position by participant to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Participants: ID, whole initiative bonus, unique tie-priority number, smaller first
A,0,1 B,0,2
Fair die sides, same for every participant
6
Probability each participant acts first
A: 0.583333333333; B: 0.416666666667
Expected finishing position by participant
A: 1.41666666667; B: 1.58333333333
Exact position distributions by participant
A: 1=0.583333333333 / 2=0.416666666667; B: 1=0.416666666667 / 2=0.583333333333

Try another scenario

Participants: ID, whole initiative bonus, unique tie-priority number, smaller first
A,0,1 B,1,2
Fair die sides, same for every participant
6
Probability each participant acts first
A: 0.416666666667; B: 0.583333333333
Expected finishing position by participant
A: 1.58333333333; B: 1.41666666667
Exact position distributions by participant
A: 1=0.416666666667 / 2=0.583333333333; B: 1=0.583333333333 / 2=0.416666666667
Calculation method

Calculation method

Probability each participant acts first

Condition on each possible own roll and count opposing rolls that act before it under score and supplied tie priority.

Expected finishing position by participant

Sum rank×probability for each participant, with first position numbered one.

Exact position distributions by participant

For each own roll convolve independent before/after indicators of other participants; sum exact integer outcome counts.

Symbols and units
a
Participants: ID, whole initiative bonus, unique tie-priority number, smaller first
b
Fair die sides, same for every participant

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • Independent fair initiative rolls with fixed integer bonuses and unique supplied tie priorities. It computes position probabilities without assuming ties disappear or inferring a named game’s initiative policy.
Are these inputs private?

These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.

Further reading

OpenStax: finite probability and sampling without replacement; rules are explicit in each worksheet ↗

Background reading; this does not imply endorsement or independent review of SumFizz.

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