Advantage-disadvantage roll calculator

Calculate at-least retained-result probability and retained-result probability distribution with your own figures.

Your numbers

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

Use at-least retained-result probability and retained-result probability distribution to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Fair die sides
6
Independent rolls
2
Retain max or min
max
Retained result at least query
5
At-least retained-result probability
0.555556
Retained-result probability distribution
1: 0.0277777777778; 2: 0.0833333333333; 3: 0.138888888889; 4: 0.194444444444; 5: 0.25; 6: 0.305555555556
Expected retained result
4.472222
Retained-result variance
1.971451

Try another scenario

Fair die sides
6
Independent rolls
2
Retain max or min
min
Retained result at least query
5
At-least retained-result probability
0.111111
Retained-result probability distribution
1: 0.305555555556; 2: 0.25; 3: 0.194444444444; 4: 0.138888888889; 5: 0.0833333333333; 6: 0.0277777777778
Expected retained result
2.527778
Retained-result variance
1.971451
Calculation method

Calculation method

At-least retained-result probability

Sum order-statistic counts at/above the target.

Retained-result probability distribution

For max use v^rolls−(v−1)^rolls; for min use (sides−v+1)^rolls−(sides−v)^rolls, all over sides^rolls.

Expected retained result

First moment of the exact retained-result distribution.

Retained-result variance

Exact second central moment; retain one result from all supplied rolls.

Symbols and units
a
Fair die sides
b
Independent rolls
c
Retain max or min
d
Retained result at least query

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 repeated rolls, retaining exactly one maximum or minimum. This generalizes an advantage/disadvantage-style rule but does not infer a named game’s cancellation, tie or critical rules.
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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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