# d12 variant

# Introduction

This is a variant of the standard d20 system put out by Wizards of the Coast. It came about while I was contemplating combat probabilities — more than that later. Anyways, the system involves rolling 2d12 for the base number rather than d20 — what that does is instead of giving a linear probability scale, a bell shaped distribution. What this does in effect is make easy things easier to do, and hard things harder to do (but not too much more as the max is 24 and getting a 20 is actually slightly easier). I’ll be posting up a table indicating the new probability scale. Now I’ve only run through a minimum of tests, so it’s not fully worked out, but I plan to continue to play with is as it seems to be working well so far.

## Probability Tables

2D12 | ||
---|---|---|

Target Number (TN) |
%Odds of rolling TN |
%Odds of rolling TN or higher |

## DC Changes

By using the d12 variant, not only does the proabability curve change from a linear curve to a bell curve, the average roll also increases from 10.5 to 13. This has the effect of making all low DC checks easier to accomplish, and conversely, high DC checks more difficult. Should one wish, the DC’s can be modified to accomodate the change. The following table shows the equivalent DC’s and their chances of success between d20 and the d12 variant.

For Armor Class, a base of 13 instead of 10 is used. Likewise for Spell save DC’s, and other similar mechanics that have a base of 10.

d20 DC |
d20 % | d12 DC |
d12 % |

5 |
80% | 8 |
81.4% |

10 |
55% | 13 |
54.6% |

12 |
45% | 14 |
46.2% |

15 |
30% | 16 |
31.5% |

16 |
25% | 17 |
25.2% |

17 |
20% | 18 |
19.6% |

18 |
15% | 19 |
14.7% |

19 |
10% | 20 |
10.5% |

20 |
5% | 22 |
4.2% |

22 |
N/A | 23 |
1.4% |

23 |
N/A | 24 |
0.7% |

25 |
N/A | 25 |
N/A |

## Criticals

** Critical Hit**:

**Weapon Critical Range Changes**

To account for the modified percentages for weapons, simply increase the minimum number needed to roll a treat by 1.

d20 Crit Range |
d20 % | d12 Crit Range |
d12 % |

16-20 |
25% | 17+ |
25.2% |

17-20 |
20% | 18+ |
19.6% |

18-20 |
15% | 19+ |
14.7% |

19-20 |
10% | 20+ |
10.5% |

20 |
5% | 21+ |
7% |