Table of Contents
What Is a D100?
A d100 (percentile die) generates a random number from 1 to 100. Physically, this is done with two d10s: one for tens, one for ones. Some 100-faced zocchihedron dice exist. The d100 is fundamental to percentile RPG systems like Call of Cthulhu and RuneQuest, where skills are rated 1-100.
Digital d100 rollers provide perfect uniformity, unlike physical zocchihedrons which may have slight manufacturing biases. Each number has exactly a 1% chance of appearing.
Rolling Methods
| Method | Description | Accuracy |
|---|---|---|
| Two d10s | Tens + ones digit | Perfect |
| Zocchihedron | 100-faced physical die | Slight bias possible |
| Digital | Computer-generated | Perfect uniformity |
Game Systems Using d100
- Call of Cthulhu: Roll under skill to succeed
- RuneQuest: Percentile skills with special/critical thresholds
- Warhammer Fantasy: Degree-of-success system
- Eclipse Phase: Blackjack-style roll-under
Probability
Frequently Asked Questions
Is 00+0 equal to 100 or 0?
Convention varies by game system. Most modern RPGs treat 00+0 as 100. Always check your specific game rules.
What is a percentile roll?
Any roll producing 1-100, directly mapping to a percentage. A skill of 65 means 65% success chance when rolling equal to or under.
Can d100 be used for random tables?
Yes. D100 tables provide 100 possible outcomes, common for random encounters, treasure, and plot hooks in RPGs.