Online Dice Roller: D&D Dice, Probability, and How Virtual Dice Work

Whether you’re playing Dungeons & Dragons, running a board game night, or just need a random number, understanding dice and probability makes the game richer.

Dice types explained

Die	Faces	Shape	Common Use
d4	4	Tetrahedron	Damage (daggers, darts)
d6	6	Cube	Most board games, ability scores
d8	8	Octahedron	Weapon damage (longsword)
d10	10	Pentagonal trapezohedron	Percentile, damage
d12	12	Dodecahedron	Great weapon damage
d20	20	Icosahedron	Attack rolls, saving throws, skill checks
d100	100	Two d10s (percentile)	Random encounters, loot tables

Probability basics

Every face of a fair die has equal probability:

• d6: each face = 1/6 = 16.67%
• d20: each face = 1/20 = 5% (natural 20!)
• 2d6: sum of 7 is most likely (6/36 = 16.67%)

Multiple dice probability:

• 2d6 sum ranges from 2–12 (avg: 7)
• 3d6 sum ranges from 3–18 (avg: 10.5)
• More dice = results cluster toward the average (bell curve)

D&D rolling explained

Advantage / Disadvantage

• Advantage: Roll 2d20, take the higher (equivalent to rolling a d20 with ~65% chance of 11+)
• Disadvantage: Roll 2d20, take the lower

Ability scores (4d6 drop lowest)

Roll 4d6, remove the lowest die, sum the remaining three. Average result: ~12.2 (vs 10.5 for 3d6).

Are virtual dice truly random?

Our dice roller uses crypto.getRandomValues() — the same cryptographic randomness used by banks and security systems. It’s based on hardware entropy (thermal noise, timing jitter) and is provably more random than physical dice, which can have manufacturing imperfections and throwing biases.

Rolling notation

Standard dice notation: XdY+Z

• X = number of dice
• Y = number of faces
• Z = modifier (added to total)

Examples: 2d6+3, 1d20+5, 4d6 (drop lowest)

Roll any combination with our Dice Roller — supports all dice types, modifiers, history tracking, and true cryptographic randomness.