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Arkham Horror Dice Roll Probabilities

This is the home page for dice probabilities for dice roll skill checks, modifiers and their combinations.

The tables are long and include odds of all permutations of the above skill modifiers for 1 - 20 dice and 1 - 5 minimum successes.

Accuracy should be quite good. The calculations were made using a combinatorics algorithm and tested by comparing the results to those made by a brute force calculation that rolled all possible dice combinations and counted each success. The latter method is limited due to time constraints -- checking all these combinations for 20 dice would likely take several thousand years! All brute force permutations were verified to be identical to their combinatorics counterparts for 1 to 4 dice (the Mandy/Bonus/One's Re-roll combo is a real hog) and some of the simpler combinations were verified for up to 5, 10 and 13 dice.

Tables have been organized into the following sets for easy lookup and analysis.

Table Sets and Downloads


Combos by Successes
Base Probabilities Bonus Probabilities One's Re-roll Base One's Re-roll Bonus Mandy Base Probabilities Mandy Bonus Probabilities Mandy One's Re-roll Base Mandy One's Re-roll Bonus
Shotgun Probabilities Shotgun Grapple Shotgun Wrestle Shotgun Grapple Wrestle Mandy Shotgun Probabilities Mandy Shotgun Grapple Mandy Shotgun Wrestle Mandy Shotgun Grapple Wrestle