Probability Analysis
Chance to roll at least Target x:
| Target | Disadv. | d20 | Advantage |
| 1 | 100% | 100% | 100% |
| 2 | 90.25% | 95% | 99.75% |
| 3 | 81.00% | 90% | 99.00% |
| 4 | 72.25% | 85% | 97.75% |
| 5 | 64.00% | 80% | 96.00% |
| 6 | 56.25% | 75% | 93.75% |
| 7 | 49.00% | 70% | 91.00% |
| 8 | 42.25% | 65% | 87.75% |
| 9 | 36.00% | 60% | 87.75% |
| 10 | 30.25% | 55% | 79.75% |
| 11 | 25.00% | 50% | 75.00% |
| 12 | 20.25% | 45% | 69.75% |
| 13 | 16.00% | 40% | 64.00% |
| 14 | 12.25% | 35% | 57.75% |
| 15 | 9.00% | 30% | 51.00% |
| 16 | 6.25% | 25% | 43.75% |
| 17 | 4.00% | 20% | 36.00% |
| 18 | 2.25% | 15% | 27.75% |
| 19 | 1.00% | 10% | 19.00% |
| 20 | 0.25% | 5% | 9.75% |
- Every additional number of the die translates to a 5% probability.
- The probability of rolling at least a 15 with disadvantage is 9, with a normal d20 is 30% and with advantage 51%.
- The effect is more pronounced the closer to the middle you get(+/-25% at 50%, which translates to a +/-5 modifier), but in general you should try to get advantage as much as possible and avoid disadvantage.
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