Dice Roller
Common Dice
Common Rolls
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Dice Notation & Probability
Dice Notation
Dice notation (also called standard dice notation) is a system to represent different combinations of dice. The format is NdX+M where:
- N = Number of dice to roll
- d = Delimiter (literally the letter "d")
- X = Number of sides on each die
- M = Modifier to add/subtract (optional)
Common Dice Types
d4 (Tetrahedron)
4-sided pyramid shape. Used for small damage dice in RPGs.
d6 (Cube)
Standard 6-sided die. Most common die in board games worldwide.
d8 (Octahedron)
8-sided die. Common for weapon damage in D&D.
d10 (Pentagonal)
10-sided die (0-9). Two d10s make percentile dice.
d12 (Dodecahedron)
12-sided die. Used for large weapons and certain spells.
d20 (Icosahedron)
20-sided die. The iconic die for skill checks and attacks in D&D.
Probability Basics
| Die | Min | Max | Average | Each Side % |
|---|---|---|---|---|
| d4 | 1 | 4 | 2.5 | 25% |
| d6 | 1 | 6 | 3.5 | 16.67% |
| d8 | 1 | 8 | 4.5 | 12.5% |
| d10 | 1 | 10 | 5.5 | 10% |
| d12 | 1 | 12 | 6.5 | 8.33% |
| d20 | 1 | 20 | 10.5 | 5% |
| d100 | 1 | 100 | 50.5 | 1% |
2d6 Probability Distribution
When rolling multiple dice, the probability distribution changes. For 2d6, the most common result is 7, not 6 or 8:
Special Rolls
Natural 20 (Nat 20)
Rolling the maximum value on a d20. Often represents a critical success. Probability: 5%
Natural 1 (Crit Fail)
Rolling a 1 on a d20. Often represents a critical failure. Probability: 5%
Advantage/Disadvantage
Roll 2d20 and take higher (advantage) or lower (disadvantage). Advantage averages ~13.8 instead of 10.5.
Percentile Dice
Two d10s (one for tens, one for ones) to generate 1-100. Also written as d100 or d%.
Random Number Generation
Physical dice use mechanical randomness. This digital dice roller uses JavaScript's Math.random() function, which provides pseudo-random numbers suitable for games and simulations. For cryptographic applications, use a cryptographically secure random number generator instead.
Frequently Asked Questions
What does dice notation like 2d6 mean?
Dice notation uses the format NdX where N is the number of dice and X is the number of sides. So 2d6 means 'roll two 6-sided dice,' 1d20 means 'roll one 20-sided die,' and 3d8+5 means 'roll three 8-sided dice and add 5 to the total.'
What is a natural 20 in D&D?
A 'natural 20' (or 'nat 20') is rolling a 20 on a d20 before any modifiers. In D&D, it often represents a critical hit or automatic success. The probability is exactly 5% (1 in 20 rolls).
What are the odds of rolling 7 with two dice?
Rolling 7 with two 6-sided dice (2d6) has the highest probability at 16.67% (6 out of 36 possible combinations). This is because there are 6 ways to make 7: 1+6, 2+5, 3+4, 4+3, 5+2, 6+1.
Is this dice roller truly random?
This digital dice roller uses JavaScript's Math.random() function for pseudo-random number generation. While not cryptographically secure, it provides excellent randomness for games and simulations - often more fair than physical dice which can have manufacturing imperfections.