Risk Battle Odds

Playing Risk recently, I lost a battle that I expected was a sure win (10 vs 4). I wondered what the probability of that loss was, and realised I had the means to work it out, so I did.

I spent an evening writing some Python code to estimate the probabilities, and also wrote an API to calculate the odds of any given battle on the fly. The results are calculated live each time - if you refresh, the numbers will be subtly different.

Hopefully it's all intuitive enough to use - enjoy!

Odds of attacking team winning (%)

# Attacking Players
1 2 3 4 5 6 7 8 9 10
# Defending Players 1 44 80 94 96 98 100 100 100 100 100
2 10 39 67 79 85 95 95 99 99 99
3 3 21 42 68 72 87 94 94 96 99
4 1 9 33 50 67 74 81 89 96 94
5 0 7 24 33 47 64 73 81 86 94
6 0 3 9 21 40 56 68 77 82 81
7 0 0 8 20 31 47 55 60 74 75
8 0 0 4 9 20 35 42 59 66 74
9 0 0 2 11 19 30 34 51 55 62
10 0 0 1 4 14 21 26 52 45 55

Analyse Specific Scenario

Attackers:
Defenders:
Repeats:

Below are the odds of having X troops remaining after the battle.
Having 0 trrops remaining indicates that this team lost the battle.