What Is a 10-Sided Die (D10)?
A 10-sided die, commonly referred to as a D10, is a pentagonal trapezohedron used extensively in tabletop role-playing games like Dungeons & Dragons, World of Darkness, and many wargames. Each face displays a number from 0 to 9 (or 1 to 10 depending on the variant). The D10 is one of the standard polyhedral dice in most RPG sets.
When two D10s are rolled together as percentile dice (D100), one represents the tens digit and the other the ones digit, generating a random number from 1 to 100. This is a fundamental mechanic in many RPG systems for skill checks and probability-based outcomes.
D10 Probability Formula
Each face of a fair D10 has an equal 10% chance of landing face-up. The expected value (mean) of a single D10 roll numbered 1-10 is 5.5. For multiple dice, the expected sum equals N x 5.5, where N is the number of dice rolled.
D10 Probability Table
| Outcome | Probability | Cumulative (<=) |
|---|---|---|
| 1 | 10.00% | 10.00% |
| 2 | 10.00% | 20.00% |
| 3 | 10.00% | 30.00% |
| 4 | 10.00% | 40.00% |
| 5 | 10.00% | 50.00% |
| 6 | 10.00% | 60.00% |
| 7 | 10.00% | 70.00% |
| 8 | 10.00% | 80.00% |
| 9 | 10.00% | 90.00% |
| 10 | 10.00% | 100.00% |
Common Uses of D10 Dice
- RPG Skill Checks: Many systems use D10 pools where players roll multiple D10s and count successes.
- Percentile Rolls: Two D10s combine to create a D100 for percentage-based probability checks.
- Wargaming: D10s determine hit probability, damage, and morale checks in miniature wargames.
- Statistics Education: D10s provide clean 10% probability increments for teaching probability concepts.
Frequently Asked Questions
Is a D10 a fair die?
Yes, a properly manufactured D10 (pentagonal trapezohedron) is a fair die where each of the 10 faces has an equal probability of 10%. The geometric shape ensures uniform distribution when rolled on a flat surface.
What is the average roll of a D10?
For a D10 numbered 1-10, the average (expected value) is (1+2+3+4+5+6+7+8+9+10)/10 = 5.5. For a D10 numbered 0-9, the average is 4.5.
How do percentile dice work?
Two D10s are rolled simultaneously. One die (often a different color or labeled with tens) represents the tens digit (00, 10, 20, ..., 90) and the other represents the ones digit (0-9). A roll of 00 and 0 typically equals 100, not 0.