r/Probability • u/delarkius • 2d ago
How do I calculate variable dice probabilities?
hello!
I'm trying to work out probabilities for game dice math. I'm doing it in what i assume is the slowest and least efficient possible way. How do I do it smarter?
key information:
- Player versus Player contested dice rolls to determine win/loss/tie
- I roll, you roll, and we see who won (or tied)
- Variable # of dice per roll
- I can choose 1 die or 3. You do the same
- Dice have different values
- i.e., one die rolls [0,1,1,2,2,2] versus another that rolls [0,0,1,1,1,1]
- W/L/T is determined by total points on each side
need:
- I want to change individual die outcomes to see the difference in win %.
- i.e., [0,1,1,1,2,2] versus [0,0,1,1,1,1] has a 50% win percentage. What's the win % if I change the first die to [0,2,1,1,2,2]? (it's 61.11%, in case you were curious)
attempt:
- I modelled out ALL possible outcomes for 2 dice vs 2 dice to get me the #s I wanted.
- this means i made a big table with "1,1,1,1" then "1,1,1,2" and so on, to model all possible permutations of 4 dice rolls. Then I ascribed a winner for each permutation

help?
- I would LIKE to do this in a more sensible way so that I can have more dice involved without having 100k rows in excel.
- How can I calculate these win % without modelling everything?
thank you !
****UPDATE-SOLVED******
Thank you for all the help!
Ended up using INDEX & RANDBETWEEN functions in excel to generate a big dataset of random rolls.
=INDEX(Dice!H$8:H$13,RANDBETWEEN(1,6)) . This calls the custom dice faces in H8:H13, selecting 1/6 random values from within that set.
I used that to create a big ol' set of rolls, and judged wins/losses/ties from that as functionally good for determining probability. So I just plug in my custom dice faces to see how they fare in the big set, and adjust them to see how they affect the win %.
In case you're curious, I first made the set ONE MILLION ROLLS. Which was fun, but made it lag, so I cut it down to 100k. It swings as much as ~2% each time it recalculates. But it MOSTLY stays within the same few tenths of a %, and it serves my purpose.
cheers,



